diff --git a/clang-tools-extra/clangd/ConfigFragment.h b/clang-tools-extra/clangd/ConfigFragment.h
--- a/clang-tools-extra/clangd/ConfigFragment.h
+++ b/clang-tools-extra/clangd/ConfigFragment.h
@@ -162,6 +162,22 @@
     /// This is checked for translation units only, not headers they include.
     /// Legal values are "Build" or "Skip".
     llvm::Optional<Located<std::string>> Background;
+    /// An external index uses data source outside of clangd itself. This is
+    /// usually prepared using clangd-indexer.
+    /// Exactly one source (File/Server) should be configured.
+    struct ExternalBlock {
+      /// Path to an index file generated by clangd-indexer. Relative paths may
+      /// be used, if config fragment is associated with a directory.
+      llvm::Optional<Located<std::string>> File;
+      /// Address and port number for a clangd-index-server. e.g.
+      /// `123.1.1.1:13337`.
+      llvm::Optional<Located<std::string>> Server;
+      /// Source root governed by this index. Default is the directory
+      /// associated with the config fragment. Absolute in case of user config
+      /// and relative otherwise. Should always use forward-slashes.
+      llvm::Optional<Located<std::string>> MountPoint;
+    };
+    llvm::Optional<Located<ExternalBlock>> External;
   };
   IndexBlock Index;
 
diff --git a/clang-tools-extra/clangd/ConfigYAML.cpp b/clang-tools-extra/clangd/ConfigYAML.cpp
--- a/clang-tools-extra/clangd/ConfigYAML.cpp
+++ b/clang-tools-extra/clangd/ConfigYAML.cpp
@@ -5,7 +5,6 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-
 #include "ConfigFragment.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallSet.h"
@@ -86,6 +85,22 @@
     DictParser Dict("Index", this);
     Dict.handle("Background",
                 [&](Node &N) { F.Background = scalarValue(N, "Background"); });
+    Dict.handle("External", [&](Node &N) {
+      Fragment::IndexBlock::ExternalBlock External;
+      parse(External, N);
+      F.External.emplace(std::move(External));
+      F.External->Range = N.getSourceRange();
+    });
+    Dict.parse(N);
+  }
+
+  void parse(Fragment::IndexBlock::ExternalBlock &F, Node &N) {
+    DictParser Dict("External", this);
+    Dict.handle("File", [&](Node &N) { F.File = scalarValue(N, "File"); });
+    Dict.handle("Server",
+                [&](Node &N) { F.Server = scalarValue(N, "Server"); });
+    Dict.handle("MountPoint",
+                [&](Node &N) { F.MountPoint = scalarValue(N, "MountPoint"); });
     Dict.parse(N);
   }
 
diff --git a/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp b/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp
--- a/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp
+++ b/clang-tools-extra/clangd/unittests/ConfigYAMLTests.cpp
@@ -10,6 +10,7 @@
 #include "ConfigFragment.h"
 #include "ConfigTesting.h"
 #include "Protocol.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/SourceMgr.h"
@@ -124,6 +125,25 @@
   ASSERT_THAT(Results, IsEmpty());
 }
 
+TEST(ParseYAML, ExternalBlock) {
+  CapturedDiags Diags;
+  Annotations YAML(R"yaml(
+Index:
+  External:
+    File: "foo"
+    Server: ^"bar"
+    MountPoint: "baz"
+  )yaml");
+  auto Results =
+      Fragment::parseYAML(YAML.code(), "config.yaml", Diags.callback());
+  ASSERT_EQ(Results.size(), 1u);
+  ASSERT_TRUE(Results[0].Index.External);
+  EXPECT_THAT(*Results[0].Index.External.getValue()->File, Val("foo"));
+  EXPECT_THAT(*Results[0].Index.External.getValue()->MountPoint, Val("baz"));
+  ASSERT_THAT(Diags.Diagnostics, IsEmpty());
+  EXPECT_THAT(*Results[0].Index.External.getValue()->Server, Val("bar"));
+}
+
 } // namespace
 } // namespace config
 } // namespace clangd