diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 42190604b3881..48e139ea9d058 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -4427,7 +4427,15 @@ const char *StyleOptionHelpDescription =
     "4. \"{key: value, ...}\" to set specific parameters, e.g.:\n"
     "   --style=\"{BasedOnStyle: llvm, IndentWidth: 8}\"";
 
-static FormatStyle::LanguageKind getLanguageByFileName(StringRef FileName) {
+static FormatStyle::LanguageKind getLanguageByFileName(StringRef &FileName) {
+  static constexpr std::array<llvm::StringLiteral, 2> TemplateSuffixes{
+      ".in",
+      ".template",
+  };
+  for (auto Suffix : TemplateSuffixes)
+    if (FileName.consume_back(Suffix))
+      break;
+
   if (FileName.ends_with(".c"))
     return FormatStyle::LK_C;
   if (FileName.ends_with(".java"))
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index abe546542b4af..457695cc09dcc 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -22354,6 +22354,7 @@ TEST_F(FormatTest, StructuredBindings) {
 
 TEST_F(FormatTest, FileAndCode) {
   EXPECT_EQ(FormatStyle::LK_C, guessLanguage("foo.c", ""));
+  EXPECT_EQ(FormatStyle::LK_C, guessLanguage("foo.c.in", ""));
   EXPECT_EQ(FormatStyle::LK_Cpp, guessLanguage("foo.cc", ""));
   EXPECT_EQ(FormatStyle::LK_ObjC, guessLanguage("foo.m", ""));
   EXPECT_EQ(FormatStyle::LK_ObjC, guessLanguage("foo.mm", ""));
@@ -22523,6 +22524,9 @@ TEST_F(FormatTest, GetLanguageByComment) {
   EXPECT_EQ(FormatStyle::LK_C,
             guessLanguage("foo.h", "// clang-format Language: C\n"
                                    "int i;"));
+  EXPECT_EQ(FormatStyle::LK_C,
+            guessLanguage("foo.h.in", "// clang-format Language: C\n"
+                                      "int i;"));
   EXPECT_EQ(FormatStyle::LK_Cpp,
             guessLanguage("foo.h", "// clang-format Language: Cpp\n"
                                    "int DoStuff(CGRect rect);"));