diff --git a/CHANGES.rst b/CHANGES.rst
index e1096c869..15bea2772 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -18,6 +18,10 @@ Deprecated
 Features added
 --------------
 
+* 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 b65b9b79f..69c9ccaa1 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``
@@ -1444,6 +1446,9 @@ Options for warning control
    .. versionadded:: 8.0
       Added ``misc.copy_overwrite``.
 
+   .. versionadded:: 8.2
+      Added ``duplicate_declaration.c`` and ``duplicate_declaration.cpp``.
+
 
 Builder options
 ===============
diff --git a/sphinx/domains/c/__init__.py b/sphinx/domains/c/__init__.py
index 48c83a731..f58e2e607 100644
--- a/sphinx/domains/c/__init__.py
+++ b/sphinx/domains/c/__init__.py
@@ -284,6 +284,8 @@ class CObject(ObjectDescription[ASTDeclaration]):
                 self.display_object_type,
                 sig,
                 location=signode,
+                type='duplicate_declaration',
+                subtype='c',
             )
 
         if ast.objectType == 'enumerator':
diff --git a/sphinx/domains/c/_symbol.py b/sphinx/domains/c/_symbol.py
index fe4c17147..d4662b07f 100644
--- a/sphinx/domains/c/_symbol.py
+++ b/sphinx/domains/c/_symbol.py
@@ -548,6 +548,8 @@ class Symbol:
                         our_child.declaration.directiveType,
                         name,
                         location=(other_child.docname, other_child.line),
+                        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 35d69de2f..7c84aac72 100644
--- a/sphinx/domains/cpp/__init__.py
+++ b/sphinx/domains/cpp/__init__.py
@@ -397,6 +397,8 @@ class CPPObject(ObjectDescription[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 fa940e71a..cd5bb1707 100644
--- a/sphinx/domains/cpp/_symbol.py
+++ b/sphinx/domains/cpp/_symbol.py
@@ -895,6 +895,8 @@ class Symbol:
                         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