diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -200,6 +200,10 @@
 
 - Implemented DR692, DR1395 and DR1432. Use the ``-fclang-abi-compat=15`` option
   to get the old partial ordering behavior regarding packs.
+- Clang's default C++/ObjC++ standard is now ``gnu++17`` instead of ``gnu++14``.
+  This means Clang will by default accept code using features from C++17 and
+  conforming GNU extensions. Projects incompatible with C++17 can add
+  ``-std=gnu++14`` to their build settings to restore the previous behaviour.
 
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Basic/LangStandards.cpp b/clang/lib/Basic/LangStandards.cpp
--- a/clang/lib/Basic/LangStandards.cpp
+++ b/clang/lib/Basic/LangStandards.cpp
@@ -75,10 +75,9 @@
     if (CLANG_DEFAULT_STD_CXX != LangStandard::lang_unspecified)
       return CLANG_DEFAULT_STD_CXX;
 
-    if (T.isDriverKit())
-      return LangStandard::lang_gnucxx17;
-    else
+    if (T.isPS())
       return LangStandard::lang_gnucxx14;
+    return LangStandard::lang_gnucxx17;
   case Language::RenderScript:
     return LangStandard::lang_c99;
   case Language::HIP:
diff --git a/clang/test/Preprocessor/lang-std.cpp b/clang/test/Preprocessor/lang-std.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Preprocessor/lang-std.cpp
@@ -0,0 +1,14 @@
+// UNSUPPORTED: default-std-cxx, ps4, ps5
+/// Test default standards when CLANG_DEFAULT_STD_CXX is unspecified.
+/// PS4/PS5 default to gnu++14.
+
+// RUN: %clang_cc1 -dM -E %s | FileCheck --check-prefix=CXX17 %s
+// RUN: %clang_cc1 -dM -E -x cuda %s | FileCheck --check-prefix=CXX14 %s
+// RUN: %clang_cc1 -dM -E -x hip %s | FileCheck --check-prefix=CXX14 %s
+
+// RUN: %clang_cc1 -dM -E -x cuda -std=c++14 %s | FileCheck --check-prefix=CXX14 %s
+// RUN: %clang_cc1 -dM -E -x hip -std=c++98 %s | FileCheck --check-prefix=CXX98 %s
+
+// CXX98: #define __cplusplus 199711L
+// CXX14: #define __cplusplus 201402L
+// CXX17: #define __cplusplus 201703L
diff --git a/clang/test/Preprocessor/lang-std.cu b/clang/test/Preprocessor/lang-std.cu
deleted file mode 100644
--- a/clang/test/Preprocessor/lang-std.cu
+++ /dev/null
@@ -1,7 +0,0 @@
-// RUN: %clang_cc1 -dM -E -x hip %s | FileCheck -check-prefix=CXX14 %s
-// RUN: %clang_cc1 -dM -E %s | FileCheck -check-prefix=CXX14 %s
-// RUN: %clang_cc1 -dM -E -std=c++98 -x hip %s | FileCheck -check-prefix=CXX98 %s
-// RUN: %clang_cc1 -dM -E -std=c++98 %s | FileCheck -check-prefix=CXX98 %s
-
-// CXX98: #define __cplusplus 199711L
-// CXX14: #define __cplusplus 201402L
diff --git a/clang/test/lit.cfg.py b/clang/test/lit.cfg.py
--- a/clang/test/lit.cfg.py
+++ b/clang/test/lit.cfg.py
@@ -131,6 +131,9 @@
 if config.clang_enable_opaque_pointers:
     config.available_features.add('enable-opaque-pointers')
 
+if config.clang_default_std_cxx != '':
+    config.available_features.add('default-std-cxx')
+
 # Set available features we allow tests to conditionalize on.
 #
 if config.clang_default_cxx_stdlib != '':
diff --git a/clang/test/lit.site.cfg.py.in b/clang/test/lit.site.cfg.py.in
--- a/clang/test/lit.site.cfg.py.in
+++ b/clang/test/lit.site.cfg.py.in
@@ -24,6 +24,7 @@
 config.clang_arcmt = @CLANG_ENABLE_ARCMT@
 config.clang_default_pie_on_linux = @CLANG_DEFAULT_PIE_ON_LINUX@
 config.clang_enable_opaque_pointers = @CLANG_ENABLE_OPAQUE_POINTERS_INTERNAL@
+config.clang_default_std_cxx = "@CLANG_DEFAULT_STD_CXX@"
 config.clang_default_cxx_stdlib = "@CLANG_DEFAULT_CXX_STDLIB@"
 config.clang_staticanalyzer = @CLANG_ENABLE_STATIC_ANALYZER@
 config.clang_staticanalyzer_z3 = @LLVM_WITH_Z3@