diff --git a/CHANGES.rst b/CHANGES.rst
index 6ab37736ff2..15bea277262 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -18,8 +18,9 @@ Deprecated
 Features added
 --------------
 
-* C: Added ``c.duplicate_declaration`` to the warning control options.
-  Patch by Julien Lecomte.
+* Add a new ``duplicate_declaration`` warning type,
+  with ``duplicate_declaration.c`` and ``duplicate_declaration.cpp`` subtypes.
+  Patch by Julien Lecomte and Adam Turner.
 
 Bugs fixed
 ----------
diff --git a/doc/usage/configuration.rst b/doc/usage/configuration.rst
index 903e1ea7d71..799897cfe14 100644
--- a/doc/usage/configuration.rst
+++ b/doc/usage/configuration.rst
@@ -1374,6 +1374,8 @@ Options for warning control
    * ``config.cache``
    * ``docutils``
    * ``download.not_readable``
+   * ``duplicate_declaration.c``
+   * ``duplicate_declaration.cpp``
    * ``epub.unknown_project_files``
    * ``epub.duplicated_toc_entry``
    * ``i18n.inconsistent_references``
@@ -1404,7 +1406,6 @@ Options for warning control
    * ``autosectionlabel.<document name>``
    * ``autosummary``
    * ``autosummary.import_cycle``
-   * ``c.duplicate_declaration``
    * ``intersphinx.external``
 
    You can choose from these types.  You can also give only the first
diff --git a/sphinx/domains/c/__init__.py b/sphinx/domains/c/__init__.py
index 4e6704972ac..f58e2e607ff 100644
--- a/sphinx/domains/c/__init__.py
+++ b/sphinx/domains/c/__init__.py
@@ -284,8 +284,8 @@ def handle_signature(self, sig: str, signode: TextElement) -> ASTDeclaration:
                 self.display_object_type,
                 sig,
                 location=signode,
-                type='c',
-                subtype='duplicate_declaration',
+                type='duplicate_declaration',
+                subtype='c',
             )
 
         if ast.objectType == 'enumerator':
diff --git a/sphinx/domains/c/_symbol.py b/sphinx/domains/c/_symbol.py
index 629cabff4cf..d4662b07fc0 100644
--- a/sphinx/domains/c/_symbol.py
+++ b/sphinx/domains/c/_symbol.py
@@ -548,8 +548,8 @@ def merge_with(
                         our_child.declaration.directiveType,
                         name,
                         location=(other_child.docname, other_child.line),
-                        type='c',
-                        subtype='duplicate_declaration',
+                        type='duplicate_declaration',
+                        subtype='c',
                     )
                 else:
                     # Both have declarations, and in the same docname.
diff --git a/sphinx/domains/cpp/__init__.py b/sphinx/domains/cpp/__init__.py
index 35d69de2fb0..7c84aac727a 100644
--- a/sphinx/domains/cpp/__init__.py
+++ b/sphinx/domains/cpp/__init__.py
@@ -397,6 +397,8 @@ def handle_signature(self, sig: str, signode: desc_signature) -> ASTDeclaration:
                 self.display_object_type,
                 sig,
                 location=signode,
+                type='duplicate_declaration',
+                subtype='cpp',
             )
 
         if ast.objectType == 'enumerator':
diff --git a/sphinx/domains/cpp/_symbol.py b/sphinx/domains/cpp/_symbol.py
index fa940e71a3f..cd5bb1707c7 100644
--- a/sphinx/domains/cpp/_symbol.py
+++ b/sphinx/domains/cpp/_symbol.py
@@ -895,6 +895,8 @@ def unconditional_add(self: Symbol, other_child: Symbol) -> None:
                         our_child.declaration.directiveType,
                         name,
                         location=(other_child.docname, other_child.line),
+                        type='duplicate_declaration',
+                        subtype='cpp',
                     )
                 else:
                     our_object_type = our_child.declaration.objectType