diff --git a/clang/include/clang/Interpreter/Interpreter.h b/clang/include/clang/Interpreter/Interpreter.h
--- a/clang/include/clang/Interpreter/Interpreter.h
+++ b/clang/include/clang/Interpreter/Interpreter.h
@@ -60,14 +60,12 @@
   const llvm::orc::LLJIT *getExecutionEngine() const;
   llvm::Expected<PartialTranslationUnit &> Parse(llvm::StringRef Code);
   llvm::Error Execute(PartialTranslationUnit &T);
-  llvm::Error ParseAndExecute(llvm::StringRef Code) {
-    auto PTU = Parse(Code);
-    if (!PTU)
-      return PTU.takeError();
-    if (PTU->TheModule)
-      return Execute(*PTU);
-    return llvm::Error::success();
-  }
+  llvm::Error ParseAndExecute(llvm::StringRef Code);
+
+  /// \returns the last PartialTranslationUnit.
+  PartialTranslationUnit &getLastPTU();
+
+  llvm::Error Undo(unsigned N = 1);
 
   /// \returns the \c JITTargetAddress of a \c GlobalDecl. This interface uses
   /// the CodeGenModule's internal mangling cache to avoid recomputing the
diff --git a/clang/lib/Interpreter/IncrementalExecutor.h b/clang/lib/Interpreter/IncrementalExecutor.h
--- a/clang/lib/Interpreter/IncrementalExecutor.h
+++ b/clang/lib/Interpreter/IncrementalExecutor.h
@@ -13,6 +13,7 @@
 #ifndef LLVM_CLANG_LIB_INTERPRETER_INCREMENTALEXECUTOR_H
 #define LLVM_CLANG_LIB_INTERPRETER_INCREMENTALEXECUTOR_H
 
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
@@ -29,11 +30,17 @@
 } // namespace llvm
 
 namespace clang {
+
+struct PartialTranslationUnit;
+
 class IncrementalExecutor {
   using CtorDtorIterator = llvm::orc::CtorDtorIterator;
   std::unique_ptr<llvm::orc::LLJIT> Jit;
   llvm::orc::ThreadSafeContext &TSCtx;
 
+  llvm::DenseMap<const PartialTranslationUnit *, llvm::orc::ResourceTrackerSP>
+      ResourceTrackers;
+
 public:
   enum SymbolNameKind { IRName, LinkerName };
 
@@ -41,7 +48,8 @@
                       const llvm::Triple &Triple);
   ~IncrementalExecutor();
 
-  llvm::Error addModule(std::unique_ptr<llvm::Module> M);
+  llvm::Error addModule(PartialTranslationUnit *PTU);
+  llvm::Error removeModule(clang::PartialTranslationUnit *PTU);
   llvm::Error runCtors() const;
   llvm::Expected<llvm::JITTargetAddress>
   getSymbolAddress(llvm::StringRef Name, SymbolNameKind NameKind) const;
diff --git a/clang/lib/Interpreter/IncrementalExecutor.cpp b/clang/lib/Interpreter/IncrementalExecutor.cpp
--- a/clang/lib/Interpreter/IncrementalExecutor.cpp
+++ b/clang/lib/Interpreter/IncrementalExecutor.cpp
@@ -12,6 +12,7 @@
 
 #include "IncrementalExecutor.h"
 
+#include "clang/Interpreter/PartialTranslationUnit.h"
 #include "llvm/ExecutionEngine/ExecutionEngine.h"
 #include "llvm/ExecutionEngine/Orc/CompileUtils.h"
 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
@@ -52,8 +53,24 @@
 
 IncrementalExecutor::~IncrementalExecutor() {}
 
-llvm::Error IncrementalExecutor::addModule(std::unique_ptr<llvm::Module> M) {
-  return Jit->addIRModule(llvm::orc::ThreadSafeModule(std::move(M), TSCtx));
+llvm::Error IncrementalExecutor::addModule(PartialTranslationUnit *PTU) {
+  llvm::orc::ResourceTrackerSP RT =
+      Jit->getMainJITDylib().createResourceTracker();
+  ResourceTrackers[PTU] = RT;
+
+  return Jit->addIRModule(RT, {std::move(PTU->TheModule), TSCtx});
+}
+
+llvm::Error IncrementalExecutor::removeModule(PartialTranslationUnit *PTU) {
+
+  llvm::orc::ResourceTrackerSP RT = std::move(ResourceTrackers[PTU]);
+  if (!RT)
+    return llvm::Error::success();
+
+  ResourceTrackers.erase(PTU);
+  if (llvm::Error Err = RT->remove())
+    return Err;
+  return llvm::Error::success();
 }
 
 llvm::Error IncrementalExecutor::runCtors() const {
diff --git a/clang/lib/Interpreter/IncrementalParser.h b/clang/lib/Interpreter/IncrementalParser.h
--- a/clang/lib/Interpreter/IncrementalParser.h
+++ b/clang/lib/Interpreter/IncrementalParser.h
@@ -72,6 +72,8 @@
   ///\returns the mangled name of a \c GD.
   llvm::StringRef GetMangledName(GlobalDecl GD) const;
 
+  std::list<PartialTranslationUnit> &getPTUs() { return PTUs; }
+
 private:
   llvm::Expected<PartialTranslationUnit &> ParseOrWrapTopLevelDecl();
 };
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -218,8 +218,7 @@
     if (Err)
       return Err;
   }
-  // FIXME: Add a callback to retain the llvm::Module once the JIT is done.
-  if (auto Err = IncrExecutor->addModule(std::move(T.TheModule)))
+  if (auto Err = IncrExecutor->addModule(&T))
     return Err;
 
   if (auto Err = IncrExecutor->runCtors())
@@ -228,6 +227,16 @@
   return llvm::Error::success();
 }
 
+llvm::Error Interpreter::ParseAndExecute(llvm::StringRef Code) {
+  auto PTU = Parse(Code);
+  if (!PTU)
+    return PTU.takeError();
+  if (PTU->TheModule) {
+    return Execute(*PTU);
+  }
+  return llvm::Error::success();
+}
+
 llvm::Expected<llvm::JITTargetAddress>
 Interpreter::getSymbolAddress(GlobalDecl GD) const {
   if (!IncrExecutor)
@@ -257,3 +266,13 @@
 
   return IncrExecutor->getSymbolAddress(Name, IncrementalExecutor::LinkerName);
 }
+
+clang::PartialTranslationUnit &Interpreter::getLastPTU() {
+  return IncrParser->getPTUs().back();
+}
+
+llvm::Error Interpreter::Undo(unsigned N) {
+  llvm::Error Err = IncrExecutor->removeModule(&IncrParser->getPTUs().back());
+  IncrParser->getPTUs().pop_back();
+  return Err;
+}
diff --git a/clang/tools/clang-repl/ClangRepl.cpp b/clang/tools/clang-repl/ClangRepl.cpp
--- a/clang/tools/clang-repl/ClangRepl.cpp
+++ b/clang/tools/clang-repl/ClangRepl.cpp
@@ -95,6 +95,11 @@
     while (llvm::Optional<std::string> Line = LE.readLine()) {
       if (*Line == "quit")
         break;
+      if (*Line == "undo") {
+        Interp->Undo();
+        continue;
+      }
+
       if (auto Err = Interp->ParseAndExecute(*Line))
         llvm::logAllUnhandledErrors(std::move(Err), llvm::errs(), "error: ");
     }
diff --git a/clang/unittests/Interpreter/InterpreterTest.cpp b/clang/unittests/Interpreter/InterpreterTest.cpp
--- a/clang/unittests/Interpreter/InterpreterTest.cpp
+++ b/clang/unittests/Interpreter/InterpreterTest.cpp
@@ -248,4 +248,23 @@
   EXPECT_EQ(42, fn(NewA));
 }
 
+TEST(InterpreterTest, UndoBasic) {
+  Args ExtraArgs = {"-Xclang", "-diagnostic-log-file", "-Xclang", "-"};
+
+  // Create the diagnostic engine with unowned consumer.
+  std::string DiagnosticOutput;
+  llvm::raw_string_ostream DiagnosticsOS(DiagnosticOutput);
+  auto DiagPrinter = std::make_unique<TextDiagnosticPrinter>(
+      DiagnosticsOS, new DiagnosticOptions());
+
+  auto Interp = createInterpreter(ExtraArgs, DiagPrinter.get());
+  auto R1 = Interp->Parse("int x = 42;");
+  EXPECT_TRUE(!!R1);
+
+  llvm::cantFail(Interp->Undo());
+
+  auto R2 = Interp->Parse("int x = 24;");
+  EXPECT_TRUE(!!R2);
+}
+
 } // end anonymous namespace