diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1778,7 +1778,7 @@
     llvm::StringRef InstallDir = getDriver().getInstalledDir();
     if (InstallDir.empty())
       break;
-    // On Darwin, libc++ may be installed alongside the compiler in
+    // On Darwin, libc++ is installed alongside the compiler in
     // include/c++/v1.
     // Get from 'foo/bin' to 'foo/include/c++/v1'.
     SmallString<128> P = InstallDir;
diff --git a/clang/lib/Frontend/InitHeaderSearch.cpp b/clang/lib/Frontend/InitHeaderSearch.cpp
--- a/clang/lib/Frontend/InitHeaderSearch.cpp
+++ b/clang/lib/Frontend/InitHeaderSearch.cpp
@@ -467,7 +467,10 @@
   if (Lang.CPlusPlus && !Lang.AsmPreprocessor &&
       HSOpts.UseStandardCXXIncludes && HSOpts.UseStandardSystemIncludes) {
     if (HSOpts.UseLibcxx) {
-      AddPath("/usr/include/c++/v1", CXXSystem, false);
+      // On Darwin, all libc++ header search paths are handled in the driver.
+      if (!triple.isOSDarwin()) {
+        AddPath("/usr/include/c++/v1", CXXSystem, false);
+      }
     } else {
       AddDefaultCPlusPlusIncludePaths(Lang, triple, HSOpts);
     }
diff --git a/clang/test/Driver/Inputs/basic_darwin_sdk/usr/bin/.keep b/clang/test/Driver/Inputs/basic_darwin_sdk/usr/bin/.keep
new file mode 100644
diff --git a/clang/test/Driver/Inputs/basic_darwin_sdk/usr/include/.keep b/clang/test/Driver/Inputs/basic_darwin_sdk/usr/include/.keep
new file mode 100644
diff --git a/clang/test/Driver/Inputs/basic_darwin_sdk/usr/lib/.keep b/clang/test/Driver/Inputs/basic_darwin_sdk/usr/lib/.keep
new file mode 100644
diff --git a/clang/test/Driver/Inputs/basic_darwin_toolchain/usr/bin/.keep b/clang/test/Driver/Inputs/basic_darwin_toolchain/usr/bin/.keep
new file mode 100644
diff --git a/clang/test/Driver/Inputs/basic_darwin_toolchain/usr/include/c++/v1/.keep b/clang/test/Driver/Inputs/basic_darwin_toolchain/usr/include/c++/v1/.keep
new file mode 100644
diff --git a/clang/test/Driver/darwin-header-search.cpp b/clang/test/Driver/darwin-header-search.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/darwin-header-search.cpp
@@ -0,0 +1,23 @@
+// General tests that the header search paths detected by the driver and passed
+// to CC1 are sane on Darwin platforms.
+
+// Check a basic invocation (the headers alongside the toolchain should be used).
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -stdlib=libc++ \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:   | FileCheck -DINPUTS=%S/Inputs --check-prefix=CHECK-BASIC-LIBCXX-ISYSTEM %s
+// CHECK-BASIC-LIBCXX-ISYSTEM: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-BASIC-LIBCXX-ISYSTEM: "-internal-isystem" "[[INPUTS]]/basic_darwin_toolchain/usr/bin/../include/c++/v1"
+
+// Check with a custom -isysroot (the headers in the toolchain should still be used).
+// RUN: %clang -no-canonical-prefixes %s -### -fsyntax-only 2>&1 \
+// RUN:     -target x86_64-apple-darwin \
+// RUN:     -stdlib=libc++ \
+// RUN:     -ccc-install-dir %S/Inputs/basic_darwin_toolchain/usr/bin \
+// RUN:     -resource-dir=%S/Inputs/resource_dir \
+// RUN:     --sysroot=%S/Inputs/basic_darwin_sdk \
+// RUN:   | FileCheck -DINPUTS=%S/Inputs --check-prefix=CHECK-BASIC-LIBCXX-ISYSTEM-WITH-SYSROOT %s
+// CHECK-BASIC-LIBCXX-ISYSTEM-WITH-SYSROOT: "{{[^"]*}}clang{{[^"]*}}" "-cc1"
+// CHECK-BASIC-LIBCXX-ISYSTEM-WITH-SYSROOT: "-internal-isystem" "[[INPUTS]]/basic_darwin_toolchain/usr/bin/../include/c++/v1"