Index: clang/tools/clang-format/clang-format-diff.py
===================================================================
--- clang/tools/clang-format/clang-format-diff.py
+++ clang/tools/clang-format/clang-format-diff.py
@@ -47,7 +47,7 @@
                       help='custom pattern selecting file paths to reformat '
                       '(case sensitive, overrides -iregex)')
   parser.add_argument('-iregex', metavar='PATTERN', default=
-                      r'.*\.(cpp|cc|c\+\+|cxx|c|cl|h|hh|hpp|hxx|m|mm|inc|js|ts'
+                      r'.*\.(cpp|cc|c\+\+|cxx|cppm|c|cl|h|hh|hpp|hxx|m|mm|inc|js|ts'
                       r'|proto|protodevel|java|cs|json)',
                       help='custom pattern selecting file paths to reformat '
                       '(case insensitive, overridden by -regex)')
Index: clang/tools/clang-format/git-clang-format
===================================================================
--- clang/tools/clang-format/git-clang-format
+++ clang/tools/clang-format/git-clang-format
@@ -78,7 +78,7 @@
       'c', 'h',  # C
       'm',  # ObjC
       'mm',  # ObjC++
-      'cc', 'cp', 'cpp', 'c++', 'cxx', 'hh', 'hpp', 'hxx',  # C++
+      'cc', 'cp', 'cpp', 'c++', 'cxx', 'hh', 'hpp', 'hxx', 'cppm',  # C++
       'cu', 'cuh',  # CUDA
       # Other languages that clang-format supports
       'proto', 'protodevel',  # Protocol Buffers