diff --git a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
--- a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
+++ b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
@@ -33,6 +33,12 @@
   return std::string(ShardRootSS.str());
 }
 
+std::string getGitignorePathForShardRoot(llvm::StringRef ShardRoot) {
+  llvm::SmallString<128> ShardRootSS(ShardRoot);
+  llvm::sys::path::append(ShardRootSS, llvm::sys::path::filename(".gitignore"));
+  return std::string(ShardRootSS.str());
+}
+
 // Uses disk as a storage for index shards.
 class DiskBackedIndexStorage : public BackgroundIndexStorage {
   std::string DiskShardRoot;
@@ -40,12 +46,21 @@
 public:
   // Creates `DiskShardRoot` and any parents during construction.
   DiskBackedIndexStorage(llvm::StringRef Directory) : DiskShardRoot(Directory) {
+    bool CreatingNewDirectory = !llvm::sys::fs::is_directory(DiskShardRoot);
     std::error_code OK;
     std::error_code EC = llvm::sys::fs::create_directories(DiskShardRoot);
     if (EC != OK) {
       elog("Failed to create directory {0} for index storage: {1}",
            DiskShardRoot, EC.message());
     }
+
+    if (CreatingNewDirectory) {
+      llvm::Error error = addGitignore(DiskShardRoot);
+      if (error) {
+        elog("Failed to add .gitignore to directory {0} for index storage: {1}",
+             DiskShardRoot, error);
+      }
+    }
   }
 
   std::unique_ptr<IndexFileIn>
@@ -73,6 +88,15 @@
                                        return llvm::Error::success();
                                      });
   }
+
+private:
+  llvm::Error addGitignore(llvm::StringRef Directory) {
+    auto FilePath = getGitignorePathForShardRoot(DiskShardRoot);
+    return llvm::writeFileAtomically(
+        FilePath + ".tmp", FilePath,
+        "# This file is autogenerated by clangd. If you change or delete it, "
+        "it won't be recreated.\n*");
+  }
 };
 
 // Doesn't persist index shards anywhere (used when the CDB dir is unknown).
diff --git a/clang-tools-extra/clangd/test/background-index.test b/clang-tools-extra/clangd/test/background-index.test
--- a/clang-tools-extra/clangd/test/background-index.test
+++ b/clang-tools-extra/clangd/test/background-index.test
@@ -18,6 +18,18 @@
 # RUN: ls %/t/.cache/clangd/index/foo.cpp.*.idx
 # RUN: ls %/t/sub_dir/.cache/clangd/index/foo.h.*.idx
 
+# Test that the the newly created index directories also have a .gitignore file present.
+# RUN: ls %/t/.cache/clangd/index/.gitignore
+# RUN: ls %/t/sub_dir/.cache/clangd/index/.gitignore
+
+# Delete .gitignore files to test that they're not recreated when loading an existing index directory.
+# RUN: rm %/t/.cache/clangd/index/.gitignore
+# RUN: rm %/t/sub_dir/.cache/clangd/index/.gitignore
+
 # Test the index is read from disk: delete code and restart clangd.
 # RUN: rm %/t/foo.cpp
 # RUN: clangd -background-index -lit-test < %/t/definition.jsonrpc | FileCheck %/t/definition.jsonrpc --check-prefixes=CHECK,USE
+
+# Test that the existing index directories do not have recreated .gitignore files.
+# RUN: test ! -e %/t/.cache/clangd/index/.gitignore
+# RUN: test ! -e %/t/sub_dir/.cache/clangd/index/.gitignore