diff --git a/clang-tools-extra/clangd/CMakeLists.txt b/clang-tools-extra/clangd/CMakeLists.txt
--- a/clang-tools-extra/clangd/CMakeLists.txt
+++ b/clang-tools-extra/clangd/CMakeLists.txt
@@ -53,6 +53,7 @@
   ConfigYAML.cpp
   Diagnostics.cpp
   DraftStore.cpp
+  DumpAST.cpp
   ExpectedTypes.cpp
   FindSymbols.cpp
   FindTarget.cpp
diff --git a/clang-tools-extra/clangd/ClangdLSPServer.h b/clang-tools-extra/clangd/ClangdLSPServer.h
--- a/clang-tools-extra/clangd/ClangdLSPServer.h
+++ b/clang-tools-extra/clangd/ClangdLSPServer.h
@@ -92,6 +92,7 @@
   void onDocumentDidChange(const DidChangeTextDocumentParams &);
   void onDocumentDidClose(const DidCloseTextDocumentParams &);
   void onDocumentDidSave(const DidSaveTextDocumentParams &);
+  void onAST(const ASTParams &, Callback<llvm::Optional<ASTNode>>);
   void onDocumentOnTypeFormatting(const DocumentOnTypeFormattingParams &,
                                   Callback<std::vector<TextEdit>>);
   void onDocumentRangeFormatting(const DocumentRangeFormattingParams &,
diff --git a/clang-tools-extra/clangd/ClangdLSPServer.cpp b/clang-tools-extra/clangd/ClangdLSPServer.cpp
--- a/clang-tools-extra/clangd/ClangdLSPServer.cpp
+++ b/clang-tools-extra/clangd/ClangdLSPServer.cpp
@@ -11,6 +11,7 @@
 #include "CodeComplete.h"
 #include "Diagnostics.h"
 #include "DraftStore.h"
+#include "DumpAST.h"
 #include "GlobalCompilationDatabase.h"
 #include "Protocol.h"
 #include "SemanticHighlighting.h"
@@ -21,6 +22,7 @@
 #include "support/Context.h"
 #include "support/MemoryTree.h"
 #include "support/Trace.h"
+#include "clang/AST/ASTContext.h"
 #include "clang/Basic/Version.h"
 #include "clang/Tooling/Core/Replacement.h"
 #include "llvm/ADT/ArrayRef.h"
@@ -610,6 +612,7 @@
             {"documentSymbolProvider", true},
             {"workspaceSymbolProvider", true},
             {"referencesProvider", true},
+            {"astProvider", true},
             {"executeCommandProvider",
              llvm::json::Object{
                  {"commands",
@@ -1383,6 +1386,11 @@
       });
 }
 
+void ClangdLSPServer::onAST(const ASTParams &Params,
+                            Callback<llvm::Optional<ASTNode>> CB) {
+  Server->getAST(Params.textDocument.uri.file(), Params.range, std::move(CB));
+}
+
 ClangdLSPServer::ClangdLSPServer(class Transport &Transp,
                                  const ThreadsafeFS &TFS,
                                  const ClangdLSPServer::Options &Opts)
@@ -1412,6 +1420,7 @@
   MsgHandler->bind("workspace/executeCommand", &ClangdLSPServer::onCommand);
   MsgHandler->bind("textDocument/documentHighlight", &ClangdLSPServer::onDocumentHighlight);
   MsgHandler->bind("workspace/symbol", &ClangdLSPServer::onWorkspaceSymbol);
+  MsgHandler->bind("textDocument/ast", &ClangdLSPServer::onAST);
   MsgHandler->bind("textDocument/didOpen", &ClangdLSPServer::onDocumentDidOpen);
   MsgHandler->bind("textDocument/didClose", &ClangdLSPServer::onDocumentDidClose);
   MsgHandler->bind("textDocument/didChange", &ClangdLSPServer::onDocumentDidChange);
diff --git a/clang-tools-extra/clangd/ClangdServer.h b/clang-tools-extra/clangd/ClangdServer.h
--- a/clang-tools-extra/clangd/ClangdServer.h
+++ b/clang-tools-extra/clangd/ClangdServer.h
@@ -319,6 +319,9 @@
   void semanticHighlights(PathRef File,
                           Callback<std::vector<HighlightingToken>>);
 
+  /// Describe the AST subtree for a piece of code.
+  void getAST(PathRef File, Range, Callback<llvm::Optional<ASTNode>>);
+
   /// Runs an arbitrary action that has access to the AST of the specified file.
   /// The action will execute on one of ClangdServer's internal threads.
   /// The AST is only valid for the duration of the callback.
diff --git a/clang-tools-extra/clangd/ClangdServer.cpp b/clang-tools-extra/clangd/ClangdServer.cpp
--- a/clang-tools-extra/clangd/ClangdServer.cpp
+++ b/clang-tools-extra/clangd/ClangdServer.cpp
@@ -9,6 +9,7 @@
 #include "ClangdServer.h"
 #include "CodeComplete.h"
 #include "Config.h"
+#include "DumpAST.h"
 #include "FindSymbols.h"
 #include "Format.h"
 #include "HeaderSourceSwitch.h"
@@ -784,6 +785,38 @@
                            TUScheduler::InvalidateOnUpdate);
 }
 
+void ClangdServer::getAST(PathRef File, Range R,
+                          Callback<llvm::Optional<ASTNode>> CB) {
+  auto Action =
+      [R, CB(std::move(CB))](llvm::Expected<InputsAndAST> Inputs) mutable {
+        if (!Inputs)
+          return CB(Inputs.takeError());
+        unsigned Start, End;
+        if (auto O = positionToOffset(Inputs->Inputs.Contents, R.start))
+          Start = *O;
+        else
+          return CB(O.takeError());
+        if (auto O = positionToOffset(Inputs->Inputs.Contents, R.end))
+          End = *O;
+        else
+          return CB(O.takeError());
+
+        bool Success = SelectionTree::createEach(
+            Inputs->AST.getASTContext(), Inputs->AST.getTokens(), Start, End,
+            [&](SelectionTree T) {
+              if (const SelectionTree::Node *N = T.commonAncestor()) {
+                CB(dumpAST(N->ASTNode, Inputs->AST.getTokens(),
+                           Inputs->AST.getASTContext()));
+                return true;
+              }
+              return false;
+            });
+        if (!Success)
+          CB(llvm::None);
+      };
+  WorkScheduler.runWithAST("GetAST", File, std::move(Action));
+}
+
 void ClangdServer::customAction(PathRef File, llvm::StringRef Name,
                                 Callback<InputsAndAST> Action) {
   WorkScheduler.runWithAST(Name, File, std::move(Action));
diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
--- a/clang-tools-extra/clangd/Protocol.h
+++ b/clang-tools-extra/clangd/Protocol.h
@@ -1576,6 +1576,45 @@
 };
 llvm::json::Value toJSON(const FoldingRange &Range);
 
+/// Payload for textDocument/ast request.
+/// This request is a clangd extension.
+struct ASTParams {
+  /// The text document.
+  TextDocumentIdentifier textDocument;
+
+  /// The position of the node to be dumped.
+  /// The highest-level node that entirely contains the range will be returned.
+  Range range;
+};
+bool fromJSON(const llvm::json::Value &, ASTParams &, llvm::json::Path);
+
+/// Simplified description of a clang AST node.
+/// This is clangd's internal representation of C++ code.
+struct ASTNode {
+  /// The general kind of node, such as "expression"
+  /// Corresponds to the base AST node type such as Expr.
+  std::string role;
+  /// The specific kind of node this is, such as "BinaryOperator".
+  /// This is usually a concrete node class (with Expr etc suffix dropped).
+  /// When there's no hierarchy (e.g. TemplateName), the variant (NameKind).
+  std::string kind;
+  /// Brief additional information, such as "||" for the particular operator.
+  /// The information included depends on the node kind, and may be empty.
+  std::string detail;
+  /// A one-line dump of detailed information about the node.
+  /// This includes role/kind/description information, but is rather cryptic.
+  /// It is similar to the output from `clang -Xclang -ast-dump`.
+  /// May be empty for certain types of nodes.
+  std::string arcana;
+  /// The range of the original source file covered by this node.
+  /// May be missing for implicit nodes, or those created by macro expansion.
+  llvm::Optional<Range> range;
+  /// Nodes nested within this one, such as the operands of a BinaryOperator.
+  std::vector<ASTNode> children;
+};
+llvm::json::Value toJSON(const ASTNode &);
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const ASTNode &);
+
 } // namespace clangd
 } // namespace clang
 
diff --git a/clang-tools-extra/clangd/Protocol.cpp b/clang-tools-extra/clangd/Protocol.cpp
--- a/clang-tools-extra/clangd/Protocol.cpp
+++ b/clang-tools-extra/clangd/Protocol.cpp
@@ -1300,5 +1300,41 @@
   return Result;
 }
 
+bool fromJSON(const llvm::json::Value &Params, ASTParams &R,
+              llvm::json::Path P) {
+  llvm::json::ObjectMapper O(Params, P);
+  return O && O.map("textDocument", R.textDocument) && O.map("range", R.range);
+}
+
+llvm::json::Value toJSON(const ASTNode &N) {
+  llvm::json::Object Result{
+      {"role", N.role},
+      {"kind", N.kind},
+  };
+  if (!N.children.empty())
+    Result["children"] = N.children;
+  if (!N.detail.empty())
+    Result["detail"] = N.detail;
+  if (!N.arcana.empty())
+    Result["arcana"] = N.arcana;
+  if (N.range)
+    Result["range"] = *N.range;
+  return Result;
+}
+
+llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const ASTNode &Root) {
+  std::function<void(const ASTNode &, unsigned)> Print = [&](const ASTNode &N,
+                                                             unsigned Level) {
+    OS.indent(2 * Level) << N.role << ": " << N.kind;
+    if (!N.detail.empty())
+      OS << " - " << N.detail;
+    OS << "\n";
+    for (const ASTNode &C : N.children)
+      Print(C, Level + 1);
+  };
+  Print(Root, 0);
+  return OS;
+}
+
 } // namespace clangd
 } // namespace clang
diff --git a/clang-tools-extra/clangd/test/initialize-params.test b/clang-tools-extra/clangd/test/initialize-params.test
--- a/clang-tools-extra/clangd/test/initialize-params.test
+++ b/clang-tools-extra/clangd/test/initialize-params.test
@@ -5,6 +5,7 @@
 # CHECK-NEXT:  "jsonrpc": "2.0",
 # CHECK-NEXT:  "result": {
 # CHECK-NEXT:    "capabilities": {
+# CHECK-NEXT:      "astProvider": true,
 # CHECK-NEXT:      "codeActionProvider": true,
 # CHECK-NEXT:      "completionProvider": {
 # CHECK-NEXT:        "allCommitCharacters": [
diff --git a/clang-tools-extra/clangd/unittests/CMakeLists.txt b/clang-tools-extra/clangd/unittests/CMakeLists.txt
--- a/clang-tools-extra/clangd/unittests/CMakeLists.txt
+++ b/clang-tools-extra/clangd/unittests/CMakeLists.txt
@@ -51,6 +51,7 @@
   DexTests.cpp
   DiagnosticsTests.cpp
   DraftStoreTests.cpp
+  DumpASTTests.cpp
   ExpectedTypeTest.cpp
   FileDistanceTests.cpp
   FileIndexTests.cpp