diff --git a/packages/pigeon/CHANGELOG.md b/packages/pigeon/CHANGELOG.md
index e70fe00a56a4..916106ed846e 100644
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 27.3.0
+
+* Adds support for sharing constants across platforms.
+
 ## 27.2.0
 
 * Adds support for empty data classes.
diff --git a/packages/pigeon/README.md b/packages/pigeon/README.md
index 1029d51f3be9..126c20df46ae 100644
--- a/packages/pigeon/README.md
+++ b/packages/pigeon/README.md
@@ -1,3 +1,4 @@
+<?code-excerpt path-base="example/app"?>
 # Pigeon
 
 Pigeon is a code generator tool to make communication between Flutter and the
@@ -82,6 +83,20 @@ the threading model for handling HostApi methods can be selected with the
 Host and Flutter APIs now support the ability to provide a unique message channel suffix string
 to the api to allow for multiple instances to be created and operate in parallel.
 
+### Constants
+
+Pigeon supports generating top-level constants in the generated files. Constants can be defined at the top level of the Pigeon file:
+
+<?code-excerpt "pigeons/messages.dart (constants)"?>
+```dart
+const String aStringConstant = 'stringConstantValue';
+const int anIntConstant = 42;
+const double aDoubleConstant = 3.14;
+const bool aBoolConstant = true;
+```
+
+These constants will be translated into static constants or final variables in the target languages (e.g., `public static final` in Java, `let` in Swift, `const` in Dart, etc.). Only `String`, `int`, `double`, and `bool` constant types are supported.
+
 ## Usage
 
 1) Add pigeon as a `dev_dependency`.
diff --git a/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java b/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java
index 75a676627eca..ae6eb680e1d2 100644
--- a/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java
+++ b/packages/pigeon/example/app/android/app/src/main/java/io/flutter/plugins/Messages.java
@@ -27,6 +27,12 @@
 /** Generated class from Pigeon. */
 @SuppressWarnings({"unused", "unchecked", "CodeBlock2Expr", "RedundantSuppression", "serial"})
 public class Messages {
+
+  public static final String aStringConstant = "stringConstantValue";
+  public static final long anIntConstant = 42L;
+  public static final double aDoubleConstant = 3.14;
+  public static final boolean aBoolConstant = true;
+
   static boolean pigeonDoubleEquals(double a, double b) {
     // Normalize -0.0 to 0.0 and handle NaN equality.
     return (a == 0.0 ? 0.0 : a) == (b == 0.0 ? 0.0 : b) || (Double.isNaN(a) && Double.isNaN(b));
diff --git a/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt b/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt
index e81766320f31..28fa69ce42b6 100644
--- a/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt
+++ b/packages/pigeon/example/app/android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt
@@ -13,6 +13,11 @@ import io.flutter.plugin.common.StandardMessageCodec
 import java.io.ByteArrayOutputStream
 import java.nio.ByteBuffer
 
+const val aStringConstant: String = "stringConstantValue"
+const val anIntConstant: Long = 42L
+const val aDoubleConstant: Double = 3.14
+const val aBoolConstant: Boolean = true
+
 private object MessagesPigeonUtils {
 
   fun createConnectionError(channelName: String): FlutterError {
diff --git a/packages/pigeon/example/app/ios/Runner/Messages.g.swift b/packages/pigeon/example/app/ios/Runner/Messages.g.swift
index 686f51fcb553..59f44d8d0094 100644
--- a/packages/pigeon/example/app/ios/Runner/Messages.g.swift
+++ b/packages/pigeon/example/app/ios/Runner/Messages.g.swift
@@ -14,6 +14,11 @@ import Foundation
   #error("Unsupported platform.")
 #endif
 
+public let aStringConstant: String = "stringConstantValue"
+public let anIntConstant: Int64 = 42
+public let aDoubleConstant: Double = 3.14
+public let aBoolConstant: Bool = true
+
 /// Error class for passing custom error details to Dart side.
 final class PigeonError: Error {
   let code: String
diff --git a/packages/pigeon/example/app/lib/src/messages.g.dart b/packages/pigeon/example/app/lib/src/messages.g.dart
index 10f648a9f714..573e95b06106 100644
--- a/packages/pigeon/example/app/lib/src/messages.g.dart
+++ b/packages/pigeon/example/app/lib/src/messages.g.dart
@@ -12,6 +12,11 @@ import 'dart:typed_data' show Float64List, Int32List, Int64List;
 import 'package:flutter/services.dart';
 import 'package:meta/meta.dart' show immutable, protected, visibleForTesting;
 
+const String aStringConstant = 'stringConstantValue';
+const int anIntConstant = 42;
+const double aDoubleConstant = 3.14;
+const bool aBoolConstant = true;
+
 Object? _extractReplyValueOrThrow(
   List<Object?>? replyList,
   String channelName, {
diff --git a/packages/pigeon/example/app/linux/messages.g.h b/packages/pigeon/example/app/linux/messages.g.h
index 45a903dbb4c2..38c85f4d1eda 100644
--- a/packages/pigeon/example/app/linux/messages.g.h
+++ b/packages/pigeon/example/app/linux/messages.g.h
@@ -11,6 +11,11 @@
 
 G_BEGIN_DECLS
 
+#define PIGEON_EXAMPLE_PACKAGE_A_STRING_CONSTANT "stringConstantValue"
+#define PIGEON_EXAMPLE_PACKAGE_AN_INT_CONSTANT 42
+#define PIGEON_EXAMPLE_PACKAGE_A_DOUBLE_CONSTANT 3.14
+#define PIGEON_EXAMPLE_PACKAGE_A_BOOL_CONSTANT TRUE
+
 /**
  * PigeonExamplePackageCode:
  * PIGEON_EXAMPLE_PACKAGE_CODE_ONE:
diff --git a/packages/pigeon/example/app/macos/Runner/messages.g.h b/packages/pigeon/example/app/macos/Runner/messages.g.h
index 3f08b096986f..c717742660c6 100644
--- a/packages/pigeon/example/app/macos/Runner/messages.g.h
+++ b/packages/pigeon/example/app/macos/Runner/messages.g.h
@@ -13,6 +13,11 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+extern NSString *const PGNAStringConstant;
+extern const NSInteger PGNAnIntConstant;
+extern const double PGNADoubleConstant;
+extern const BOOL PGNABoolConstant;
+
 typedef NS_ENUM(NSUInteger, PGNCode) {
   PGNCodeOne = 0,
   PGNCodeTwo = 1,
diff --git a/packages/pigeon/example/app/macos/Runner/messages.g.m b/packages/pigeon/example/app/macos/Runner/messages.g.m
index 10334a87e855..606315747e5c 100644
--- a/packages/pigeon/example/app/macos/Runner/messages.g.m
+++ b/packages/pigeon/example/app/macos/Runner/messages.g.m
@@ -12,6 +12,10 @@
 @import Flutter;
 #endif
 
+NSString *const PGNAStringConstant = @"stringConstantValue";
+const NSInteger PGNAnIntConstant = 42;
+const double PGNADoubleConstant = 3.14;
+const BOOL PGNABoolConstant = YES;
 static BOOL __attribute__((unused)) FLTPigeonDeepEquals(id _Nullable a, id _Nullable b) {
   if (a == b) {
     return YES;
diff --git a/packages/pigeon/example/app/pigeons/messages.dart b/packages/pigeon/example/app/pigeons/messages.dart
index 585fe650e3e7..48bbc026c534 100644
--- a/packages/pigeon/example/app/pigeons/messages.dart
+++ b/packages/pigeon/example/app/pigeons/messages.dart
@@ -63,3 +63,10 @@ abstract class MessageFlutterApi {
 }
 
 // #enddocregion flutter-definitions
+
+// #docregion constants
+const String aStringConstant = 'stringConstantValue';
+const int anIntConstant = 42;
+const double aDoubleConstant = 3.14;
+const bool aBoolConstant = true;
+// #enddocregion constants
diff --git a/packages/pigeon/example/app/windows/runner/messages.g.h b/packages/pigeon/example/app/windows/runner/messages.g.h
index 2ad87b1205df..22756881cc41 100644
--- a/packages/pigeon/example/app/windows/runner/messages.g.h
+++ b/packages/pigeon/example/app/windows/runner/messages.g.h
@@ -20,6 +20,11 @@ namespace pigeon_example {
 
 // Generated class from Pigeon.
 
+inline constexpr const char* aStringConstant = "stringConstantValue";
+inline constexpr int64_t anIntConstant = 42;
+inline constexpr double aDoubleConstant = 3.14;
+inline constexpr bool aBoolConstant = true;
+
 class FlutterError {
  public:
   explicit FlutterError(const std::string& code) : code_(code) {}
diff --git a/packages/pigeon/lib/src/ast.dart b/packages/pigeon/lib/src/ast.dart
index 0ae00783b7df..8b23bef2e73f 100644
--- a/packages/pigeon/lib/src/ast.dart
+++ b/packages/pigeon/lib/src/ast.dart
@@ -785,6 +785,38 @@ class EnumMember extends Node {
   }
 }
 
+/// Represents a constant.
+class Constant extends Node {
+  /// Parametric constructor for [Constant].
+  Constant({
+    required this.name,
+    required this.type,
+    required this.value,
+    this.offset,
+    this.documentationComments = const <String>[],
+  });
+
+  /// The name of the constant.
+  final String name;
+
+  /// The type of the constant.
+  final TypeDeclaration type;
+
+  /// The value of the constant.
+  final Object value;
+
+  /// The offset in the source file where the constant appears.
+  final int? offset;
+
+  /// List of documentation comments, separated by line.
+  final List<String> documentationComments;
+
+  @override
+  String toString() {
+    return '(Constant name:$name type:$type value:$value documentationComments:$documentationComments)';
+  }
+}
+
 /// Top-level node for the AST.
 class Root extends Node {
   /// Parametric constructor for [Root].
@@ -792,6 +824,7 @@ class Root extends Node {
     required this.classes,
     required this.apis,
     required this.enums,
+    this.constants = const <Constant>[],
     this.containsHostApi = false,
     this.containsFlutterApi = false,
     this.containsProxyApi = false,
@@ -800,7 +833,7 @@ class Root extends Node {
 
   /// Factory function for generating an empty root, usually used when early errors are encountered.
   factory Root.makeEmpty() {
-    return Root(apis: <Api>[], classes: <Class>[], enums: <Enum>[]);
+    return Root(apis: <Api>[], classes: <Class>[], enums: <Enum>[], constants: <Constant>[]);
   }
 
   // TODO(tarrinneal): Ensure classes are sorted in topological dependency order; see
@@ -814,6 +847,9 @@ class Root extends Node {
   /// All of the enums contained in the AST.
   List<Enum> enums;
 
+  /// All of the constants contained in the AST.
+  List<Constant> constants;
+
   /// Whether the root has any Host API definitions.
   bool containsHostApi;
 
@@ -835,6 +871,6 @@ class Root extends Node {
 
   @override
   String toString() {
-    return '(Root classes:$classes apis:$apis enums:$enums)';
+    return '(Root classes:$classes apis:$apis enums:$enums constants:$constants)';
   }
 }
diff --git a/packages/pigeon/lib/src/cpp/cpp_generator.dart b/packages/pigeon/lib/src/cpp/cpp_generator.dart
index 36bc99653a12..156643c2aa47 100644
--- a/packages/pigeon/lib/src/cpp/cpp_generator.dart
+++ b/packages/pigeon/lib/src/cpp/cpp_generator.dart
@@ -817,6 +817,30 @@ $friendLines
 ''');
   }
 
+  @override
+  void writeConstants(
+    InternalCppOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, _docCommentSpec);
+      final String type = constant.type.baseName;
+      if (type == 'String') {
+        final String escaped = escapeStringDoubleQuotes(constant.value.toString());
+        indent.writeln('inline constexpr const char* ${constant.name} = "$escaped";');
+      } else {
+        final String cppType = _baseCppTypeForBuiltinDartType(constant.type) ?? 'auto';
+        indent.writeln('inline constexpr $cppType ${constant.name} = ${constant.value};');
+      }
+    }
+  }
+
   @override
   void writeCloseNamespace(
     InternalCppOptions generatorOptions,
diff --git a/packages/pigeon/lib/src/dart/dart_generator.dart b/packages/pigeon/lib/src/dart/dart_generator.dart
index 94fe726ea933..58355db8a448 100644
--- a/packages/pigeon/lib/src/dart/dart_generator.dart
+++ b/packages/pigeon/lib/src/dart/dart_generator.dart
@@ -186,6 +186,65 @@ class DartGenerator extends StructuredGenerator<InternalDartOptions> {
     indent.writeln("import 'package:meta/meta.dart' show immutable, protected, visibleForTesting;");
   }
 
+  @override
+  void writeConstants(
+    InternalDartOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, docCommentSpec);
+      final String formattedValue = _formatValue(constant.type.baseName, constant.value);
+      indent.writeln('const ${constant.type.baseName} ${constant.name} = $formattedValue;');
+    }
+  }
+
+  String _formatValue(String type, Object value) =>
+      type == 'String' ? _makeDartStringLiteral(value.toString()) : value.toString();
+
+  String _makeDartStringLiteral(String valStr) {
+    final bool hasSpecial =
+        valStr.contains(r'\') ||
+        valStr.contains(r'$') ||
+        valStr.contains('\n') ||
+        valStr.contains('\r');
+
+    if (!hasSpecial) {
+      if (!valStr.contains("'")) {
+        return "'$valStr'";
+      }
+      if (!valStr.contains('"')) {
+        return '"$valStr"';
+      }
+      return "'${escapeStringSingleQuotes(valStr)}'";
+    }
+
+    if (!valStr.contains('\n') && !valStr.contains('\r')) {
+      if (!valStr.contains("'")) {
+        return "r'$valStr'";
+      }
+      if (!valStr.contains('"')) {
+        return 'r"$valStr"';
+      }
+      return "'${escapeStringSingleQuotes(valStr)}'";
+    }
+
+    if (!valStr.contains("'''")) {
+      return "r'''$valStr'''";
+    }
+    if (!valStr.contains('"""')) {
+      return 'r"""$valStr"""';
+    }
+
+    final String escaped = escapeStringSingleQuotes(valStr);
+    return "'$escaped'";
+  }
+
   @override
   void writeEnum(
     InternalDartOptions generatorOptions,
diff --git a/packages/pigeon/lib/src/generator.dart b/packages/pigeon/lib/src/generator.dart
index f1e2568749f9..f263bda3f57f 100644
--- a/packages/pigeon/lib/src/generator.dart
+++ b/packages/pigeon/lib/src/generator.dart
@@ -37,6 +37,8 @@ abstract class StructuredGenerator<T extends InternalOptions> extends Generator<
 
     writeOpenNamespace(generatorOptions, root, indent, dartPackageName: dartPackageName);
 
+    writeConstants(generatorOptions, root, indent, dartPackageName: dartPackageName);
+
     writeGeneralUtilities(generatorOptions, root, indent, dartPackageName: dartPackageName);
 
     if (root.apis.any((Api api) => api is AstProxyApi)) {
@@ -106,6 +108,16 @@ abstract class StructuredGenerator<T extends InternalOptions> extends Generator<
     required String dartPackageName,
   }) {}
 
+  /// Writes all constants to [indent].
+  ///
+  /// This method is not required, and does not need to be overridden.
+  void writeConstants(
+    T generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {}
+
   /// Writes all enums to [indent].
   ///
   /// Can be overridden to add extra code before/after enums.
diff --git a/packages/pigeon/lib/src/generator_tools.dart b/packages/pigeon/lib/src/generator_tools.dart
index 1f3f71af1f12..0438945a8edc 100644
--- a/packages/pigeon/lib/src/generator_tools.dart
+++ b/packages/pigeon/lib/src/generator_tools.dart
@@ -15,7 +15,7 @@ import 'generator.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '27.2.0';
+const String pigeonVersion = '27.3.0';
 
 /// Default plugin package name.
 const String defaultPluginPackageName = 'dev.flutter.pigeon';
@@ -871,3 +871,22 @@ bool isCollectionType(TypeDeclaration type) {
       !type.isProxyApi &&
       (type.baseName.contains('List') || type.baseName == 'Map');
 }
+
+/// Escapes special characters in a string for use in double-quoted string literals.
+String escapeStringDoubleQuotes(String value) {
+  return value
+      .replaceAll(r'\', r'\\')
+      .replaceAll('"', r'\"')
+      .replaceAll('\n', r'\n')
+      .replaceAll('\r', r'\r');
+}
+
+/// Escapes special characters in a string for use in single-quoted string literals.
+String escapeStringSingleQuotes(String value) {
+  return value
+      .replaceAll(r'\', r'\\')
+      .replaceAll("'", r"\'")
+      .replaceAll('\n', r'\n')
+      .replaceAll('\r', r'\r')
+      .replaceAll(r'$', r'\$');
+}
diff --git a/packages/pigeon/lib/src/gobject/gobject_generator.dart b/packages/pigeon/lib/src/gobject/gobject_generator.dart
index ce01cfccdfa1..cf643c2b9295 100644
--- a/packages/pigeon/lib/src/gobject/gobject_generator.dart
+++ b/packages/pigeon/lib/src/gobject/gobject_generator.dart
@@ -198,6 +198,36 @@ class GObjectHeaderGenerator extends StructuredGenerator<InternalGObjectOptions>
     indent.writeln('G_BEGIN_DECLS');
   }
 
+  @override
+  void writeConstants(
+    InternalGObjectOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    final String module = _getModule(generatorOptions, dartPackageName);
+    final String moduleScreaming = toScreamingSnakeCase(module);
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, _docCommentSpec);
+      final String constantName = toScreamingSnakeCase(constant.name);
+      final String type = constant.type.baseName;
+      final String valueStr;
+      if (type == 'String') {
+        final String escaped = escapeStringDoubleQuotes(constant.value.toString());
+        valueStr = '"$escaped"';
+      } else if (type == 'bool') {
+        valueStr = (constant.value as bool) ? 'TRUE' : 'FALSE';
+      } else {
+        valueStr = constant.value.toString();
+      }
+      indent.writeln('#define ${moduleScreaming}_$constantName $valueStr');
+    }
+  }
+
   @override
   void writeEnum(
     InternalGObjectOptions generatorOptions,
diff --git a/packages/pigeon/lib/src/java/java_generator.dart b/packages/pigeon/lib/src/java/java_generator.dart
index e0854b438d9d..b72e1a5f1c1c 100644
--- a/packages/pigeon/lib/src/java/java_generator.dart
+++ b/packages/pigeon/lib/src/java/java_generator.dart
@@ -200,11 +200,34 @@ class JavaGenerator extends StructuredGenerator<InternalJavaOptions> {
     }
     indent.writeln('public class ${generatorOptions.className!} {');
     indent.inc();
-    _writeNumberHelpers(indent);
-    _writeDeepEquals(indent);
-    _writeDeepHashCode(indent);
   }
 
+  @override
+  void writeConstants(
+    InternalJavaOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, _docCommentSpec);
+      final String javaType =
+          _javaTypeForBuiltinDartType(constant.type, primitive: true) ?? 'Object';
+      final String formattedValue = _formatJavaValue(constant.type.baseName, constant.value);
+      indent.writeln('public static final $javaType ${constant.name} = $formattedValue;');
+    }
+  }
+
+  String _formatJavaValue(String type, Object value) => switch (type) {
+    'String' => '"${escapeStringDoubleQuotes(value.toString())}"',
+    'int' => '${value}L',
+    _ => value.toString(),
+  };
+
   @override
   void writeEnum(
     InternalJavaOptions generatorOptions,
@@ -1326,6 +1349,10 @@ protected static ArrayList<Object> wrapError(@NonNull Throwable exception) {
     Indent indent, {
     required String dartPackageName,
   }) {
+    indent.newln();
+    _writeNumberHelpers(indent);
+    _writeDeepEquals(indent);
+    _writeDeepHashCode(indent);
     indent.newln();
     _writeErrorClass(indent);
     if (root.containsHostApi) {
@@ -1391,7 +1418,17 @@ String _javaTypeForBuiltinGenericDartType(TypeDeclaration type, int numberTypeAr
   }
 }
 
-String? _javaTypeForBuiltinDartType(TypeDeclaration type) {
+String? _javaTypeForBuiltinDartType(TypeDeclaration type, {bool primitive = false}) {
+  if (primitive) {
+    switch (type.baseName) {
+      case 'bool':
+        return 'boolean';
+      case 'int':
+        return 'long';
+      case 'double':
+        return 'double';
+    }
+  }
   const javaTypeForDartTypeMap = <String, String>{
     'bool': 'Boolean',
     'int': 'Long',
diff --git a/packages/pigeon/lib/src/kotlin/kotlin_generator.dart b/packages/pigeon/lib/src/kotlin/kotlin_generator.dart
index 9354fb3928ee..646a5cc6481a 100644
--- a/packages/pigeon/lib/src/kotlin/kotlin_generator.dart
+++ b/packages/pigeon/lib/src/kotlin/kotlin_generator.dart
@@ -239,6 +239,31 @@ class KotlinGenerator extends StructuredGenerator<InternalKotlinOptions> {
     }
   }
 
+  @override
+  void writeConstants(
+    InternalKotlinOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, _docCommentSpec);
+      final String kotlinType = _kotlinTypeForBuiltinDartType(constant.type) ?? 'Any';
+      final String formattedValue = _formatKotlinValue(constant.type.baseName, constant.value);
+      indent.writeln('const val ${constant.name}: $kotlinType = $formattedValue');
+    }
+  }
+
+  String _formatKotlinValue(String type, Object value) => switch (type) {
+    'String' => '"${escapeStringDoubleQuotes(value.toString()).replaceAll(r'$', r'\$')}"',
+    'int' => '${value}L',
+    _ => value.toString(),
+  };
+
   @override
   void writeEnum(
     InternalKotlinOptions generatorOptions,
diff --git a/packages/pigeon/lib/src/objc/objc_generator.dart b/packages/pigeon/lib/src/objc/objc_generator.dart
index b922a2f702e1..6c2311a862ce 100644
--- a/packages/pigeon/lib/src/objc/objc_generator.dart
+++ b/packages/pigeon/lib/src/objc/objc_generator.dart
@@ -206,6 +206,32 @@ class ObjcHeaderGenerator extends StructuredGenerator<InternalObjcOptions> {
     indent.writeln('NS_ASSUME_NONNULL_BEGIN');
   }
 
+  @override
+  void writeConstants(
+    InternalObjcOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, _docCommentSpec);
+      final String constantName = _constantName(generatorOptions.prefix, constant.name);
+      final String type = constant.type.baseName;
+      if (type == 'String') {
+        indent.writeln('extern NSString *const $constantName;');
+      } else if (type == 'bool') {
+        indent.writeln('extern const BOOL $constantName;');
+      } else {
+        final _ObjcType objcType = _objcTypeForDartType(generatorOptions.prefix, constant.type);
+        indent.writeln('extern const $objcType $constantName;');
+      }
+    }
+  }
+
   @override
   void writeEnum(
     InternalObjcOptions generatorOptions,
@@ -467,8 +493,33 @@ class ObjcSourceGenerator extends StructuredGenerator<InternalObjcOptions> {
     indent.writeln('@import Flutter;');
     indent.writeln('#endif');
     indent.newln();
-    _writeDeepEquals(indent);
-    _writeDeepHash(indent);
+  }
+
+  @override
+  void writeConstants(
+    InternalObjcOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      final String constantName = _constantName(generatorOptions.prefix, constant.name);
+      final String type = constant.type.baseName;
+      if (type == 'String') {
+        final String escaped = escapeStringDoubleQuotes(constant.value.toString());
+        indent.writeln('NSString *const $constantName = @"$escaped";');
+      } else if (type == 'bool') {
+        final boolVal = (constant.value as bool) ? 'YES' : 'NO';
+        indent.writeln('const BOOL $constantName = $boolVal;');
+      } else {
+        final _ObjcType objcType = _objcTypeForDartType(generatorOptions.prefix, constant.type);
+        indent.writeln('const $objcType $constantName = ${constant.value};');
+      }
+    }
   }
 
   @override
@@ -1007,6 +1058,9 @@ if (self.wrapped == nil) {
     Indent indent, {
     required String dartPackageName,
   }) {
+    _writeDeepEquals(indent);
+    _writeDeepHash(indent);
+    indent.newln();
     if (root.containsHostApi) {
       _writeWrapError(indent);
       indent.newln();
@@ -1437,6 +1491,15 @@ String _className(String? prefix, String className) {
   }
 }
 
+/// Calculates the ObjC constant name, converting to UpperCamelCase when prefixed.
+String _constantName(String? prefix, String constantName) {
+  if (prefix != null && prefix.isNotEmpty) {
+    return '$prefix${toUpperCamelCase(constantName)}';
+  } else {
+    return constantName;
+  }
+}
+
 /// Calculates callback block signature for async methods.
 String _callbackForType(TypeDeclaration type, _ObjcType objcType, InternalObjcOptions options) {
   if (type.isVoid) {
diff --git a/packages/pigeon/lib/src/pigeon_lib_internal.dart b/packages/pigeon/lib/src/pigeon_lib_internal.dart
index 756451173d34..d1a12fd93988 100644
--- a/packages/pigeon/lib/src/pigeon_lib_internal.dart
+++ b/packages/pigeon/lib/src/pigeon_lib_internal.dart
@@ -1094,6 +1094,7 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
   final List<Api> _apis = <Api>[];
   final List<Enum> _enums = <Enum>[];
   final List<Class> _classes = <Class>[];
+  final List<Constant> _constants = <Constant>[];
   final List<Error> _errors = <Error>[];
 
   /// Input file location.
@@ -1157,6 +1158,7 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
       apis: _apis,
       classes: _classes,
       enums: referencedEnums,
+      constants: _constants,
       containsHostApi: containsHostApi,
       containsFlutterApi: containsFlutterApi,
       containsProxyApi: containsProxyApi,
@@ -1216,6 +1218,38 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     final List<Error> validateErrors = _validateAst(completeRoot, source);
     totalErrors.addAll(validateErrors);
 
+    final allowedValueValidators = <String, bool Function(Object?)>{
+      'String': (Object? v) => v is String,
+      'int': (Object? v) => v is int,
+      'double': (Object? v) => v is num,
+      'bool': (Object? v) => v is bool,
+    };
+    for (final Constant constant in _constants) {
+      final String typeName = constant.type.baseName;
+      final bool Function(Object?)? validator = allowedValueValidators[typeName];
+      if (validator == null) {
+        totalErrors.add(
+          Error(
+            message:
+                'Unsupported constant type: "$typeName". Only String, int, double, and bool are supported.',
+            lineNumber: constant.offset != null
+                ? calculateLineNumber(source, constant.offset!)
+                : null,
+          ),
+        );
+      } else if (!validator(constant.value)) {
+        totalErrors.add(
+          Error(
+            message:
+                'Constant "${constant.name}" type is $typeName but value is ${constant.value.runtimeType}.',
+            lineNumber: constant.offset != null
+                ? calculateLineNumber(source, constant.offset!)
+                : null,
+          ),
+        );
+      }
+    }
+
     return ParseResults(
       root: totalErrors.isEmpty
           ? completeRoot
@@ -1354,6 +1388,133 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     return null;
   }
 
+  @override
+  Object? visitTopLevelVariableDeclaration(dart_ast.TopLevelVariableDeclaration node) {
+    if (node.variables.isConst) {
+      final dart_ast.TypeAnnotation? typeAnnotation = node.variables.type;
+      if (typeAnnotation == null) {
+        _errors.add(
+          Error(
+            message: 'Top-level constants must have an explicit type annotation.',
+            lineNumber: calculateLineNumber(source, node.offset),
+          ),
+        );
+        return null;
+      }
+      if (typeAnnotation is! dart_ast.NamedType) {
+        _errors.add(
+          Error(
+            message: 'Top-level constants must have a named type annotation.',
+            lineNumber: calculateLineNumber(source, node.offset),
+          ),
+        );
+        return null;
+      }
+      for (final dart_ast.VariableDeclaration variable in node.variables.variables) {
+        final dart_ast.Expression? initializer = variable.initializer;
+        if (initializer == null) {
+          _errors.add(
+            Error(
+              message: 'Top-level constant "${variable.name.lexeme}" must have an initializer.',
+              lineNumber: calculateLineNumber(source, variable.offset),
+            ),
+          );
+          continue;
+        }
+
+        Object? value = _evaluateExpression(initializer);
+        if (value == null) {
+          continue;
+        }
+
+        if (_getNamedTypeQualifiedName(typeAnnotation) == 'double' && value is num) {
+          value = value.toDouble();
+        }
+
+        final type = TypeDeclaration(
+          baseName: _getNamedTypeQualifiedName(typeAnnotation),
+          isNullable: typeAnnotation.question != null,
+          typeArguments: _typeAnnotationsToTypeArguments(typeAnnotation.typeArguments),
+        );
+
+        _constants.add(
+          Constant(
+            name: variable.name.lexeme,
+            type: type,
+            value: value,
+            offset: variable.offset,
+            documentationComments: _documentationCommentsParser(node.documentationComment?.tokens),
+          ),
+        );
+      }
+    }
+    node.visitChildren(this);
+    return null;
+  }
+
+  Object? _evaluateExpression(dart_ast.Expression expression) {
+    if (expression is dart_ast.SimpleStringLiteral) {
+      return expression.value;
+    } else if (expression is dart_ast.IntegerLiteral) {
+      return expression.value!;
+    } else if (expression is dart_ast.DoubleLiteral) {
+      return expression.value;
+    } else if (expression is dart_ast.BooleanLiteral) {
+      return expression.value;
+    } else if (expression is dart_ast.PrefixExpression) {
+      final Object? operandValue = _evaluateExpression(expression.operand);
+      if (operandValue == null) {
+        return null;
+      }
+      final String operator = expression.operator.lexeme;
+      if (operator == '-') {
+        if (operandValue is int) {
+          return -operandValue;
+        } else if (operandValue is double) {
+          return -operandValue;
+        }
+      } else if (operator == '!') {
+        if (operandValue is bool) {
+          return !operandValue;
+        }
+      }
+      _errors.add(
+        Error(
+          message: 'Unsupported prefix operator "$operator" on type "${operandValue.runtimeType}".',
+          lineNumber: calculateLineNumber(source, expression.offset),
+        ),
+      );
+      return null;
+    } else if (expression is dart_ast.AdjacentStrings) {
+      final buffer = StringBuffer();
+      for (final dart_ast.StringLiteral literal in expression.strings) {
+        final Object? val = _evaluateExpression(literal);
+        if (val is! String) {
+          return null;
+        }
+        buffer.write(val);
+      }
+      return buffer.toString();
+    } else if (expression is dart_ast.StringInterpolation) {
+      _errors.add(
+        Error(
+          message: 'String interpolation is not supported in Pigeon constants.',
+          lineNumber: calculateLineNumber(source, expression.offset),
+        ),
+      );
+      return null;
+    } else {
+      _errors.add(
+        Error(
+          message:
+              'Unsupported expression type ${expression.runtimeType} for constant initializer.',
+          lineNumber: calculateLineNumber(source, expression.offset),
+        ),
+      );
+      return null;
+    }
+  }
+
   @override
   Object? visitAnnotation(dart_ast.Annotation node) {
     if (node.name.name == 'ConfigurePigeon') {
diff --git a/packages/pigeon/lib/src/swift/swift_generator.dart b/packages/pigeon/lib/src/swift/swift_generator.dart
index 248ce1a18abc..200460ff145d 100644
--- a/packages/pigeon/lib/src/swift/swift_generator.dart
+++ b/packages/pigeon/lib/src/swift/swift_generator.dart
@@ -223,6 +223,34 @@ class SwiftGenerator extends StructuredGenerator<InternalSwiftOptions> {
 #endif''');
   }
 
+  @override
+  void writeConstants(
+    InternalSwiftOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    if (root.constants.isEmpty) {
+      return;
+    }
+    indent.newln();
+    for (final Constant constant in root.constants) {
+      addDocumentationComments(indent, constant.documentationComments, _docCommentSpec);
+      final String swiftType = _swiftTypeForDartType(constant.type);
+      final String formattedValue = _formatSwiftValue(constant.type.baseName, constant.value);
+      indent.writeln('public let ${constant.name}: $swiftType = $formattedValue');
+    }
+  }
+
+  String _formatSwiftValue(String type, Object value) {
+    if (type == 'String') {
+      final String escaped = escapeStringDoubleQuotes(value.toString());
+      return '"$escaped"';
+    } else {
+      return value.toString();
+    }
+  }
+
   @override
   void writeEnum(
     InternalSwiftOptions generatorOptions,
diff --git a/packages/pigeon/pigeons/core_tests.dart b/packages/pigeon/pigeons/core_tests.dart
index 381c3d0b5f23..385e9a258a02 100644
--- a/packages/pigeon/pigeons/core_tests.dart
+++ b/packages/pigeon/pigeons/core_tests.dart
@@ -4,6 +4,12 @@
 
 import 'package:pigeon/pigeon.dart';
 
+const String aStringConstant = 'stringConstantValue';
+const String aStringConstantWithEscapes = r'''string\'\"\$ConstantValue''';
+const int anIntConstant = 42;
+const double aDoubleConstant = 3.14;
+const bool aBoolConstant = true;
+
 enum AnEnum { one, two, three, fortyTwo, fourHundredTwentyTwo }
 
 // Enums require special logic, having multiple ensures that the logic can be
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
index 868874c99ee2..547a2395c228 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/main/java/com/example/alternate_language_test_plugin/CoreTests.java
@@ -31,6 +31,13 @@
 /** Generated class from Pigeon. */
 @SuppressWarnings({"unused", "unchecked", "CodeBlock2Expr", "RedundantSuppression", "serial"})
 public class CoreTests {
+
+  public static final String aStringConstant = "stringConstantValue";
+  public static final String aStringConstantWithEscapes = "string\\'\\\"\\$ConstantValue";
+  public static final long anIntConstant = 42L;
+  public static final double aDoubleConstant = 3.14;
+  public static final boolean aBoolConstant = true;
+
   static boolean pigeonDoubleEquals(double a, double b) {
     // Normalize -0.0 to 0.0 and handle NaN equality.
     return (a == 0.0 ? 0.0 : a) == (b == 0.0 ? 0.0 : b) || (Double.isNaN(a) && Double.isNaN(b));
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/DataClassMethodsTest.java b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/DataClassMethodsTest.java
index 7b0c28355014..4c680ff923d3 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/DataClassMethodsTest.java
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/android/src/test/java/com/example/alternate_language_test_plugin/DataClassMethodsTest.java
@@ -405,4 +405,13 @@ public void nestedZeroArrayEquality() {
     assertEquals(a, b);
     assertEquals(a.hashCode(), b.hashCode());
   }
+
+  @Test
+  public void testConstants() {
+    assertEquals("stringConstantValue", CoreTests.aStringConstant);
+    assertEquals("string\\'\\\"\\$ConstantValue", CoreTests.aStringConstantWithEscapes);
+    assertEquals(42L, CoreTests.anIntConstant);
+    assertEquals(3.14, CoreTests.aDoubleConstant, 0.0001);
+    assertTrue(CoreTests.aBoolConstant);
+  }
 }
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/CoreTests.gen.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/CoreTests.gen.m
index 60799e5a6a9d..26d7d40054b7 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/CoreTests.gen.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/CoreTests.gen.m
@@ -13,6 +13,11 @@
 @import Flutter;
 #endif
 
+NSString *const FLTAStringConstant = @"stringConstantValue";
+NSString *const FLTAStringConstantWithEscapes = @"string\\'\\\"\\$ConstantValue";
+const NSInteger FLTAnIntConstant = 42;
+const double FLTADoubleConstant = 3.14;
+const BOOL FLTABoolConstant = YES;
 static BOOL __attribute__((unused)) FLTPigeonDeepEquals(id _Nullable a, id _Nullable b) {
   if (a == b) {
     return YES;
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/include/alternate_language_test_plugin/CoreTests.gen.h b/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/include/alternate_language_test_plugin/CoreTests.gen.h
index 6dc4e807620d..9ec9e3a03eca 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/include/alternate_language_test_plugin/CoreTests.gen.h
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/darwin/alternate_language_test_plugin/Sources/alternate_language_test_plugin/include/alternate_language_test_plugin/CoreTests.gen.h
@@ -14,6 +14,12 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+extern NSString *const FLTAStringConstant;
+extern NSString *const FLTAStringConstantWithEscapes;
+extern const NSInteger FLTAnIntConstant;
+extern const double FLTADoubleConstant;
+extern const BOOL FLTABoolConstant;
+
 typedef NS_ENUM(NSUInteger, FLTAnEnum) {
   FLTAnEnumOne = 0,
   FLTAnEnumTwo = 1,
diff --git a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/DataClassMethodsTest.m b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/DataClassMethodsTest.m
index 68e655ec0dca..7f9d2b004ac0 100644
--- a/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/DataClassMethodsTest.m
+++ b/packages/pigeon/platform_tests/alternate_language_test_plugin/example/ios/RunnerTests/DataClassMethodsTest.m
@@ -253,4 +253,12 @@ - (void)testNSNullPropertyEquality {
   XCTAssertEqual(a.hash, b.hash);
 }
 
+- (void)testConstants {
+  XCTAssertEqualObjects(FLTAStringConstant, @"stringConstantValue");
+  XCTAssertEqualObjects(FLTAStringConstantWithEscapes, @"string\\'\\\"\\$ConstantValue");
+  XCTAssertEqual(FLTAnIntConstant, 42);
+  XCTAssertEqual(FLTADoubleConstant, 3.14);
+  XCTAssertEqual(FLTABoolConstant, YES);
+}
+
 @end
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
index 5c24c9716589..27a2068871ac 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/integration_tests.dart
@@ -2798,6 +2798,14 @@ void runPigeonIntegrationTests(TargetGenerator targetGenerator) {
     await completer1.future;
     await completer2.future;
   }, skip: !eventChannelSupported.contains(targetGenerator));
+
+  testWidgets('constants are generated correctly', (WidgetTester _) async {
+    expect(aStringConstant, 'stringConstantValue');
+    expect(aStringConstantWithEscapes, r'''string\'\"\$ConstantValue''');
+    expect(anIntConstant, 42);
+    expect(aDoubleConstant, 3.14);
+    expect(aBoolConstant, true);
+  });
 }
 
 class _FlutterApiTestImplementation implements FlutterIntegrationCoreApi {
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
index 7f0a46e303fb..1fb7bb6fb76a 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
@@ -13,6 +13,12 @@ import 'dart:typed_data' show Float64List, Int32List, Int64List;
 import 'package:flutter/services.dart';
 import 'package:meta/meta.dart' show immutable, protected, visibleForTesting;
 
+const String aStringConstant = 'stringConstantValue';
+const String aStringConstantWithEscapes = 'string\\\'\\"\\\$ConstantValue';
+const int anIntConstant = 42;
+const double aDoubleConstant = 3.14;
+const bool aBoolConstant = true;
+
 Object? _extractReplyValueOrThrow(
   List<Object?>? replyList,
   String channelName, {
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/data_class_methods_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/data_class_methods_test.dart
index 1327fbc2b333..2af927ba3120 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/test/data_class_methods_test.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/data_class_methods_test.dart
@@ -200,6 +200,14 @@ void main() {
       );
     });
 
+    test('constants', () {
+      expect(aStringConstant, 'stringConstantValue');
+      expect(aStringConstantWithEscapes, r'''string\'\"\$ConstantValue''');
+      expect(anIntConstant, 42);
+      expect(aDoubleConstant, 3.14);
+      expect(aBoolConstant, true);
+    });
+
     test('AnEmptyClass basic methods', () {
       final a = AnEmptyClass();
       final b = AnEmptyClass();
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
index 25ff604c6dea..576574f882a3 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/main/kotlin/com/example/test_plugin/CoreTests.gen.kt
@@ -16,6 +16,12 @@ import io.flutter.plugin.common.StandardMessageCodec
 import java.io.ByteArrayOutputStream
 import java.nio.ByteBuffer
 
+const val aStringConstant: String = "stringConstantValue"
+const val aStringConstantWithEscapes: String = "string\\'\\\"\\\$ConstantValue"
+const val anIntConstant: Long = 42L
+const val aDoubleConstant: Double = 3.14
+const val aBoolConstant: Boolean = true
+
 private object CoreTestsPigeonUtils {
 
   fun createConnectionError(channelName: String): FlutterError {
diff --git a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/DataClassMethodsTest.kt b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/DataClassMethodsTest.kt
index ab9a69d91208..72eea8565991 100644
--- a/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/DataClassMethodsTest.kt
+++ b/packages/pigeon/platform_tests/test_plugin/android/src/test/kotlin/com/example/test_plugin/DataClassMethodsTest.kt
@@ -303,4 +303,13 @@ internal class DataClassMethodsTest {
         "AllNullableTypes(aNullableBool=false, aNullableInt=1234, aNullableInt64=null, aNullableDouble=2.0, aNullableByteArray=[1, 2, 3, 4], aNullable4ByteArray=[1, 2, 3, 4], aNullable8ByteArray=[1, 2, 3, 4], aNullableFloatArray=[0.5, 0.25, 1.5, 1.25], aNullableEnum=TWO, anotherNullableEnum=JUST_IN_CASE, aNullableString=hello, aNullableObject=0, allNullableTypes=null, list=[1, 2, 3], stringList=[string, another one], intList=[1, 2], doubleList=[1.1, 2.2], boolList=[true, false], enumList=[ONE, TWO], objectList=[1, 2, 3], listList=[[string, another one], [string, another one]], mapList=[{hello=1234}, {hello=1234}], recursiveClassList=null, map={hello=1234}, stringMap={hello=you}, intMap={1=0}, enumMap={ONE=FORTY_TWO, TWO=FOUR_HUNDRED_TWENTY_TWO}, objectMap={hello=1234}, listMap={1=[string, another one]}, mapMap={1={}}, recursiveClassMap=null)",
         everything.toString())
   }
+
+  @Test
+  fun testConstants() {
+    assertEquals("stringConstantValue", aStringConstant)
+    assertEquals("string\\'\\\"\\\$ConstantValue", aStringConstantWithEscapes)
+    assertEquals(42L, anIntConstant)
+    assertEquals(3.14, aDoubleConstant, 0.0)
+    assertEquals(true, aBoolConstant)
+  }
 }
diff --git a/packages/pigeon/platform_tests/test_plugin/darwin/test_plugin/Sources/test_plugin/CoreTests.gen.swift b/packages/pigeon/platform_tests/test_plugin/darwin/test_plugin/Sources/test_plugin/CoreTests.gen.swift
index 1afcdbd7453c..91af587825a1 100644
--- a/packages/pigeon/platform_tests/test_plugin/darwin/test_plugin/Sources/test_plugin/CoreTests.gen.swift
+++ b/packages/pigeon/platform_tests/test_plugin/darwin/test_plugin/Sources/test_plugin/CoreTests.gen.swift
@@ -15,6 +15,12 @@ import Foundation
   #error("Unsupported platform.")
 #endif
 
+public let aStringConstant: String = "stringConstantValue"
+public let aStringConstantWithEscapes: String = "string\\'\\\"\\$ConstantValue"
+public let anIntConstant: Int64 = 42
+public let aDoubleConstant: Double = 3.14
+public let aBoolConstant: Bool = true
+
 /// Error class for passing custom error details to Dart side.
 final class PigeonError: Error {
   let code: String
diff --git a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/DataClassMethodsTests.swift b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/DataClassMethodsTests.swift
index 69360f095190..87122369f2d0 100644
--- a/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/DataClassMethodsTests.swift
+++ b/packages/pigeon/platform_tests/test_plugin/example/ios/RunnerTests/DataClassMethodsTests.swift
@@ -383,4 +383,13 @@ struct DataClassMethodsTests {
 
     #expect(hashA == hashB)
   }
+
+  @Test
+  func testConstants() {
+    #expect(aStringConstant == "stringConstantValue")
+    #expect(aStringConstantWithEscapes == "string\\'\\\"\\$ConstantValue")
+    #expect(anIntConstant == 42)
+    #expect(aDoubleConstant == 3.14)
+    #expect(aBoolConstant == true)
+  }
 }
diff --git a/packages/pigeon/platform_tests/test_plugin/linux/pigeon/core_tests.gen.h b/packages/pigeon/platform_tests/test_plugin/linux/pigeon/core_tests.gen.h
index d3de994f5927..6ca8abdf7c02 100644
--- a/packages/pigeon/platform_tests/test_plugin/linux/pigeon/core_tests.gen.h
+++ b/packages/pigeon/platform_tests/test_plugin/linux/pigeon/core_tests.gen.h
@@ -12,6 +12,13 @@
 
 G_BEGIN_DECLS
 
+#define CORE_TESTS_PIGEON_TEST_A_STRING_CONSTANT "stringConstantValue"
+#define CORE_TESTS_PIGEON_TEST_A_STRING_CONSTANT_WITH_ESCAPES \
+  "string\\'\\\"\\$ConstantValue"
+#define CORE_TESTS_PIGEON_TEST_AN_INT_CONSTANT 42
+#define CORE_TESTS_PIGEON_TEST_A_DOUBLE_CONSTANT 3.14
+#define CORE_TESTS_PIGEON_TEST_A_BOOL_CONSTANT TRUE
+
 /**
  * CoreTestsPigeonTestAnEnum:
  * PIGEON_INTEGRATION_TESTS_AN_ENUM_ONE:
diff --git a/packages/pigeon/platform_tests/test_plugin/linux/test/data_class_methods_test.cc b/packages/pigeon/platform_tests/test_plugin/linux/test/data_class_methods_test.cc
index 0346da708dec..8a03cb66da36 100644
--- a/packages/pigeon/platform_tests/test_plugin/linux/test/data_class_methods_test.cc
+++ b/packages/pigeon/platform_tests/test_plugin/linux/test/data_class_methods_test.cc
@@ -303,3 +303,12 @@ TEST(Equality, ToStringSnapshot) {
 
   g_free(str);
 }
+
+TEST(Constants, VerifyConstants) {
+  EXPECT_STREQ(CORE_TESTS_PIGEON_TEST_A_STRING_CONSTANT, "stringConstantValue");
+  EXPECT_STREQ(CORE_TESTS_PIGEON_TEST_A_STRING_CONSTANT_WITH_ESCAPES,
+               "string\\'\\\"\\$ConstantValue");
+  EXPECT_EQ(CORE_TESTS_PIGEON_TEST_AN_INT_CONSTANT, 42);
+  EXPECT_DOUBLE_EQ(CORE_TESTS_PIGEON_TEST_A_DOUBLE_CONSTANT, 3.14);
+  EXPECT_TRUE(CORE_TESTS_PIGEON_TEST_A_BOOL_CONSTANT);
+}
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
index 521cddded991..a93faee6c5a2 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
+++ b/packages/pigeon/platform_tests/test_plugin/windows/pigeon/core_tests.gen.h
@@ -23,6 +23,13 @@ class CoreTestsTest;
 
 // Generated class from Pigeon.
 
+inline constexpr const char* aStringConstant = "stringConstantValue";
+inline constexpr const char* aStringConstantWithEscapes =
+    "string\\'\\\"\\$ConstantValue";
+inline constexpr int64_t anIntConstant = 42;
+inline constexpr double aDoubleConstant = 3.14;
+inline constexpr bool aBoolConstant = true;
+
 class FlutterError {
  public:
   explicit FlutterError(const std::string& code) : code_(code) {}
diff --git a/packages/pigeon/platform_tests/test_plugin/windows/test/data_class_methods_test.cpp b/packages/pigeon/platform_tests/test_plugin/windows/test/data_class_methods_test.cpp
index dc1f6ad3f809..7dbe007b7d1e 100644
--- a/packages/pigeon/platform_tests/test_plugin/windows/test/data_class_methods_test.cpp
+++ b/packages/pigeon/platform_tests/test_plugin/windows/test/data_class_methods_test.cpp
@@ -153,5 +153,14 @@ TEST(SerializationTests, StreamOutputFullSnapshot) {
       "map_map: null, recursive_class_map: null)");
 }
 
+TEST(ConstantTests, VerifyConstants) {
+  EXPECT_EQ(std::string(aStringConstant), "stringConstantValue");
+  EXPECT_EQ(std::string(aStringConstantWithEscapes),
+            "string\\'\\\"\\$ConstantValue");
+  EXPECT_EQ(anIntConstant, 42);
+  EXPECT_DOUBLE_EQ(aDoubleConstant, 3.14);
+  EXPECT_EQ(aBoolConstant, true);
+}
+
 }  // namespace test
 }  // namespace test_plugin
diff --git a/packages/pigeon/pubspec.yaml b/packages/pigeon/pubspec.yaml
index 8103bc0b2e72..af91648dcb59 100644
--- a/packages/pigeon/pubspec.yaml
+++ b/packages/pigeon/pubspec.yaml
@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 27.2.0 # This must match the version in lib/src/generator_tools.dart
+version: 27.3.0 # This must match the version in lib/src/generator_tools.dart
 
 environment:
   sdk: ^3.10.0
diff --git a/packages/pigeon/test/cpp_generator_test.dart b/packages/pigeon/test/cpp_generator_test.dart
index fa65936598ca..cab245024fcb 100644
--- a/packages/pigeon/test/cpp_generator_test.dart
+++ b/packages/pigeon/test/cpp_generator_test.dart
@@ -2388,4 +2388,50 @@ void main() {
       expect(code, contains('size_t Input::Hash() const {'));
     }
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const generator = CppGenerator();
+    final generatorOptions = OutputFileOptions<InternalCppOptions>(
+      fileType: FileType.header,
+      languageOptions: const InternalCppOptions(
+        headerIncludePath: 'foo.h',
+        cppHeaderOut: '',
+        cppSourceOut: '',
+      ),
+    );
+    generator.generate(generatorOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('inline constexpr const char* stringConst = "hello";'));
+    expect(code, contains('inline constexpr int64_t intConst = 42;'));
+    expect(code, contains('inline constexpr double doubleConst = 3.14;'));
+    expect(code, contains('inline constexpr bool boolConst = true;'));
+  });
 }
diff --git a/packages/pigeon/test/dart_generator_test.dart b/packages/pigeon/test/dart_generator_test.dart
index dce12d0c2034..8925c9aaf583 100644
--- a/packages/pigeon/test/dart_generator_test.dart
+++ b/packages/pigeon/test/dart_generator_test.dart
@@ -2067,4 +2067,47 @@ name: foobar
     expect(code, contains('String toString() {'));
     expect(code, contains(r"return 'Foobar(field1: $field1)';"));
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const generator = DartGenerator();
+    generator.generate(
+      const InternalDartOptions(ignoreLints: false),
+      root,
+      sink,
+      dartPackageName: DEFAULT_PACKAGE_NAME,
+    );
+    final code = sink.toString();
+    expect(code, contains("const String stringConst = 'hello';"));
+    expect(code, contains('const int intConst = 42;'));
+    expect(code, contains('const double doubleConst = 3.14;'));
+    expect(code, contains('const bool boolConst = true;'));
+  });
 }
diff --git a/packages/pigeon/test/gobject_generator_test.dart b/packages/pigeon/test/gobject_generator_test.dart
index 23e4f77f1244..566892ed5246 100644
--- a/packages/pigeon/test/gobject_generator_test.dart
+++ b/packages/pigeon/test/gobject_generator_test.dart
@@ -936,4 +936,50 @@ void main() {
     expect(code, contains('gchar* test_package_input_to_string('));
     expect(code, contains('g_string_new("Input(");'));
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const generator = GObjectGenerator();
+    final generatorOptions = OutputFileOptions<InternalGObjectOptions>(
+      fileType: FileType.header,
+      languageOptions: const InternalGObjectOptions(
+        headerIncludePath: 'foo.h',
+        gobjectHeaderOut: '',
+        gobjectSourceOut: '',
+      ),
+    );
+    generator.generate(generatorOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('#define TEST_PACKAGE_STRING_CONST "hello"'));
+    expect(code, contains('#define TEST_PACKAGE_INT_CONST 42'));
+    expect(code, contains('#define TEST_PACKAGE_DOUBLE_CONST 3.14'));
+    expect(code, contains('#define TEST_PACKAGE_BOOL_CONST TRUE'));
+  });
 }
diff --git a/packages/pigeon/test/java_generator_test.dart b/packages/pigeon/test/java_generator_test.dart
index 6a93704be7a5..6d2a58420463 100644
--- a/packages/pigeon/test/java_generator_test.dart
+++ b/packages/pigeon/test/java_generator_test.dart
@@ -1582,4 +1582,43 @@ void main() {
     expect(code, contains('public String toString() {'));
     expect(code, contains('return "Foobar{" + "field1=" + field1 + "}";'));
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const javaOptions = InternalJavaOptions(className: 'Messages', javaOut: '');
+    const generator = JavaGenerator();
+    generator.generate(javaOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('public static final String stringConst = "hello";'));
+    expect(code, contains('public static final long intConst = 42L;'));
+    expect(code, contains('public static final double doubleConst = 3.14;'));
+    expect(code, contains('public static final boolean boolConst = true;'));
+  });
 }
diff --git a/packages/pigeon/test/kotlin_generator_test.dart b/packages/pigeon/test/kotlin_generator_test.dart
index 5164c203860e..4daaadba5b79 100644
--- a/packages/pigeon/test/kotlin_generator_test.dart
+++ b/packages/pigeon/test/kotlin_generator_test.dart
@@ -1827,4 +1827,55 @@ void main() {
     expect(code, contains('override fun toString(): String {'));
     expect(code, contains(r'return "Foobar(field1=$field1, field2=$field2)"'));
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+        Constant(
+          name: 'stringWithBackslashDollar',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: r'\$',
+        ),
+        Constant(
+          name: 'stringWithTwoBackslashesDollar',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: r'\\$',
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const kotlinOptions = InternalKotlinOptions(kotlinOut: '');
+    const generator = KotlinGenerator();
+    generator.generate(kotlinOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('const val stringConst: String = "hello"'));
+    expect(code, contains('const val intConst: Long = 42L'));
+    expect(code, contains('const val doubleConst: Double = 3.14'));
+    expect(code, contains('const val boolConst: Boolean = true'));
+    expect(code, contains(r'const val stringWithBackslashDollar: String = "\\\$"'));
+    expect(code, contains(r'const val stringWithTwoBackslashesDollar: String = "\\\\\$"'));
+  });
 }
diff --git a/packages/pigeon/test/objc_generator_test.dart b/packages/pigeon/test/objc_generator_test.dart
index a5f8179fe84c..a93f3270b9d2 100644
--- a/packages/pigeon/test/objc_generator_test.dart
+++ b/packages/pigeon/test/objc_generator_test.dart
@@ -3548,4 +3548,98 @@ void main() {
     expect(code, contains('- (NSString *)description {'));
     expect(code, contains('return [NSString stringWithFormat:@"ABCFoo()"];'));
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const generator = ObjcGenerator();
+    final generatorOptions = OutputFileOptions<InternalObjcOptions>(
+      fileType: FileType.header,
+      languageOptions: const InternalObjcOptions(
+        prefix: 'ABC',
+        objcHeaderOut: '',
+        objcSourceOut: '',
+        headerIncludePath: '',
+      ),
+    );
+    generator.generate(generatorOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('extern NSString *const ABCStringConst;'));
+    expect(code, contains('extern const NSInteger ABCIntConst;'));
+    expect(code, contains('extern const double ABCDoubleConst;'));
+    expect(code, contains('extern const BOOL ABCBoolConst;'));
+  });
+
+  test('gen constants source', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const generator = ObjcGenerator();
+    final generatorOptions = OutputFileOptions<InternalObjcOptions>(
+      fileType: FileType.source,
+      languageOptions: const InternalObjcOptions(
+        prefix: 'ABC',
+        objcHeaderOut: '',
+        objcSourceOut: '',
+        headerIncludePath: '',
+      ),
+    );
+    generator.generate(generatorOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('NSString *const ABCStringConst = @"hello";'));
+    expect(code, contains('const NSInteger ABCIntConst = 42;'));
+    expect(code, contains('const double ABCDoubleConst = 3.14;'));
+    expect(code, contains('const BOOL ABCBoolConst = YES;'));
+  });
 }
diff --git a/packages/pigeon/test/pigeon_lib_test.dart b/packages/pigeon/test/pigeon_lib_test.dart
index 0273624ee61b..e8df30b2ec13 100644
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@@ -1888,4 +1888,118 @@ abstract class Api {
       await completer.future;
     });
   });
+
+  group('constants parsing', () {
+    test('valid constants', () {
+      const code = '''
+const String myString = 'hello';
+const int myInt = 42;
+const double myDouble = 3.14;
+const bool myBool = true;
+const int myNegativeInt = -10;
+const double myNegativeDouble = -2.5;
+const String myAdjacentString = 'hello ' 'world';
+''';
+      final ParseResults parseResult = parseSource(code);
+      expect(parseResult.errors, isEmpty);
+      expect(parseResult.root.constants.length, 7);
+
+      final Constant myString = parseResult.root.constants[0];
+      expect(myString.name, 'myString');
+      expect(myString.type.baseName, 'String');
+      expect(myString.value, 'hello');
+
+      final Constant myInt = parseResult.root.constants[1];
+      expect(myInt.name, 'myInt');
+      expect(myInt.type.baseName, 'int');
+      expect(myInt.value, 42);
+
+      final Constant myDouble = parseResult.root.constants[2];
+      expect(myDouble.name, 'myDouble');
+      expect(myDouble.type.baseName, 'double');
+      expect(myDouble.value, 3.14);
+
+      final Constant myBool = parseResult.root.constants[3];
+      expect(myBool.name, 'myBool');
+      expect(myBool.type.baseName, 'bool');
+      expect(myBool.value, true);
+
+      final Constant myNegativeInt = parseResult.root.constants[4];
+      expect(myNegativeInt.name, 'myNegativeInt');
+      expect(myNegativeInt.type.baseName, 'int');
+      expect(myNegativeInt.value, -10);
+
+      final Constant myNegativeDouble = parseResult.root.constants[5];
+      expect(myNegativeDouble.name, 'myNegativeDouble');
+      expect(myNegativeDouble.type.baseName, 'double');
+      expect(myNegativeDouble.value, -2.5);
+
+      final Constant myAdjacentString = parseResult.root.constants[6];
+      expect(myAdjacentString.name, 'myAdjacentString');
+      expect(myAdjacentString.type.baseName, 'String');
+      expect(myAdjacentString.value, 'hello world');
+    });
+
+    test('missing type annotation error', () {
+      const code = '''
+const myConst = 42;
+''';
+      final ParseResults parseResult = parseSource(code);
+      expect(parseResult.errors, isNotEmpty);
+      expect(
+        parseResult.errors[0].message,
+        contains('Top-level constants must have an explicit type annotation.'),
+      );
+    });
+
+    test('unsupported constant type error', () {
+      const code = '''
+const List<int> myConst = 42;
+''';
+      final ParseResults parseResult = parseSource(code);
+      expect(parseResult.errors, isNotEmpty);
+      expect(
+        parseResult.errors[0].message,
+        contains(
+          'Unsupported constant type: "List". Only String, int, double, and bool are supported.',
+        ),
+      );
+    });
+
+    test('constant value type mismatch error', () {
+      const code = '''
+const String myConst = 42;
+''';
+      final ParseResults parseResult = parseSource(code);
+      expect(parseResult.errors, isNotEmpty);
+      expect(
+        parseResult.errors[0].message,
+        contains('Constant "myConst" type is String but value is int.'),
+      );
+    });
+
+    test('unsupported expression type error', () {
+      const code = '''
+const int myConst = 1 + 2;
+''';
+      final ParseResults parseResult = parseSource(code);
+      expect(parseResult.errors, isNotEmpty);
+      expect(
+        parseResult.errors[0].message,
+        contains('Unsupported expression type BinaryExpressionImpl for constant initializer.'),
+      );
+    });
+
+    test('string interpolation error', () {
+      const code = r'''
+const String myConst = 'hello ${1 + 2}';
+''';
+      final ParseResults parseResult = parseSource(code);
+      expect(parseResult.errors, isNotEmpty);
+      expect(
+        parseResult.errors[0].message,
+        contains('String interpolation is not supported in Pigeon constants.'),
+      );
+    });
+  });
 }
diff --git a/packages/pigeon/test/swift_generator_test.dart b/packages/pigeon/test/swift_generator_test.dart
index 5c5f0417fe15..31032779c9d6 100644
--- a/packages/pigeon/test/swift_generator_test.dart
+++ b/packages/pigeon/test/swift_generator_test.dart
@@ -1537,4 +1537,43 @@ void main() {
     expect(code, contains('public var description: String {'));
     expect(code, contains(r'return "Foobar(field1: \(String(describing: field1)))"'));
   });
+
+  test('gen constants', () {
+    final root = Root(
+      apis: <Api>[],
+      classes: <Class>[],
+      enums: <Enum>[],
+      constants: <Constant>[
+        Constant(
+          name: 'stringConst',
+          type: const TypeDeclaration(baseName: 'String', isNullable: false),
+          value: 'hello',
+        ),
+        Constant(
+          name: 'intConst',
+          type: const TypeDeclaration(baseName: 'int', isNullable: false),
+          value: 42,
+        ),
+        Constant(
+          name: 'doubleConst',
+          type: const TypeDeclaration(baseName: 'double', isNullable: false),
+          value: 3.14,
+        ),
+        Constant(
+          name: 'boolConst',
+          type: const TypeDeclaration(baseName: 'bool', isNullable: false),
+          value: true,
+        ),
+      ],
+    );
+    final sink = StringBuffer();
+    const swiftOptions = InternalSwiftOptions(swiftOut: '');
+    const generator = SwiftGenerator();
+    generator.generate(swiftOptions, root, sink, dartPackageName: DEFAULT_PACKAGE_NAME);
+    final code = sink.toString();
+    expect(code, contains('let stringConst: String = "hello"'));
+    expect(code, contains('let intConst: Int64 = 42'));
+    expect(code, contains('let doubleConst: Double = 3.14'));
+    expect(code, contains('let boolConst: Bool = true'));
+  });
 }