diff --git a/crates/ruff_linter/resources/test/fixtures/ruff/RUF012.py b/crates/ruff_linter/resources/test/fixtures/ruff/RUF012.py
index e5ec4d610ba517..af37af2333fb67 100644
--- a/crates/ruff_linter/resources/test/fixtures/ruff/RUF012.py
+++ b/crates/ruff_linter/resources/test/fixtures/ruff/RUF012.py
@@ -150,3 +150,42 @@ class S(ctypes.Structure):
         ("propagation", ctypes.c_uint64),
         ("userns_fd", ctypes.c_uint64),
     ]
+
+class LES(ctypes.LittleEndianStructure):
+    test = [""]
+    _fields_ = [
+        ("attr_set", ctypes.c_uint64),
+        ("attr_clr", ctypes.c_uint64),
+        ("propagation", ctypes.c_uint64),
+        ("userns_fd", ctypes.c_uint64),
+    ]
+
+class BES(ctypes.BigEndianStructure):
+    test = [""]
+    _fields_ = [
+        ("attr_set", ctypes.c_uint64),
+        ("attr_clr", ctypes.c_uint64),
+        ("propagation", ctypes.c_uint64),
+        ("userns_fd", ctypes.c_uint64),
+    ]
+
+class U(ctypes.Union):
+    test = [""]
+    _fields_ = [
+        ("a", LES),
+        ("b", BES),
+    ]
+
+class LEU(ctypes.LittleEndianUnion):
+    test = [""]
+    _fields_ = [
+        ("a", LES),
+        ("b", BES),
+    ]
+
+class BEU(ctypes.BigEndianUnion):
+    test = [""]
+    _fields_ = [
+        ("a", LES),
+        ("b", BES),
+    ]
diff --git a/crates/ruff_linter/src/rules/ruff/helpers.rs b/crates/ruff_linter/src/rules/ruff/helpers.rs
index ba28950a92d54e..a6ebb82fb16bbe 100644
--- a/crates/ruff_linter/src/rules/ruff/helpers.rs
+++ b/crates/ruff_linter/src/rules/ruff/helpers.rs
@@ -252,7 +252,18 @@ pub(super) fn is_ctypes_structure_fields(
 ) -> bool {
     let is_ctypes_structure =
         analyze::class::any_qualified_base_class(class_def, semantic, |qualified_name| {
-            matches!(qualified_name.segments(), ["ctypes", "Structure"])
+            matches!(
+                qualified_name.segments(),
+                [
+                    "ctypes",
+                    "Structure"
+                        | "BigEndianStructure"
+                        | "LittleEndianStructure"
+                        | "Union"
+                        | "BigEndianUnion"
+                        | "LittleEndianUnion"
+                ]
+            )
         });
 
     let is_fields = matches!(
diff --git a/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF012_RUF012.py.snap b/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF012_RUF012.py.snap
index 5cc2fd8c41a52f..fdd09af79c1c94 100644
--- a/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF012_RUF012.py.snap
+++ b/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF012_RUF012.py.snap
@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/ruff/mod.rs
+assertion_line: 133
 ---
 RUF012 Mutable default value for class attribute
   --> RUF012.py:9:34
@@ -139,3 +140,58 @@ RUF012 Mutable default value for class attribute
 148 |         ("attr_set", ctypes.c_uint64),
     |
 help: Consider initializing in `__init__` or annotating with `typing.ClassVar`
+
+RUF012 Mutable default value for class attribute
+   --> RUF012.py:155:12
+    |
+154 | class LES(ctypes.LittleEndianStructure):
+155 |     test = [""]
+    |            ^^^^
+156 |     _fields_ = [
+157 |         ("attr_set", ctypes.c_uint64),
+    |
+help: Consider initializing in `__init__` or annotating with `typing.ClassVar`
+
+RUF012 Mutable default value for class attribute
+   --> RUF012.py:164:12
+    |
+163 | class BES(ctypes.BigEndianStructure):
+164 |     test = [""]
+    |            ^^^^
+165 |     _fields_ = [
+166 |         ("attr_set", ctypes.c_uint64),
+    |
+help: Consider initializing in `__init__` or annotating with `typing.ClassVar`
+
+RUF012 Mutable default value for class attribute
+   --> RUF012.py:173:12
+    |
+172 | class U(ctypes.Union):
+173 |     test = [""]
+    |            ^^^^
+174 |     _fields_ = [
+175 |         ("a", LES),
+    |
+help: Consider initializing in `__init__` or annotating with `typing.ClassVar`
+
+RUF012 Mutable default value for class attribute
+   --> RUF012.py:180:12
+    |
+179 | class LEU(ctypes.LittleEndianUnion):
+180 |     test = [""]
+    |            ^^^^
+181 |     _fields_ = [
+182 |         ("a", LES),
+    |
+help: Consider initializing in `__init__` or annotating with `typing.ClassVar`
+
+RUF012 Mutable default value for class attribute
+   --> RUF012.py:187:12
+    |
+186 | class BEU(ctypes.BigEndianUnion):
+187 |     test = [""]
+    |            ^^^^
+188 |     _fields_ = [
+189 |         ("a", LES),
+    |
+help: Consider initializing in `__init__` or annotating with `typing.ClassVar`