diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -201,6 +201,14 @@
 
    ISO C++ 2023 with amendments and GNU extensions
 
+  | ``c++2c``
+
+   ISO C++ Working draft for ISO C++ 2026
+
+  | ``gnu++2c``
+
+   ISO Working draft for ISO C++ 2026 with GNU extensions
+
  The default C++ language standard is ``gnu++17``.
 
  Supported values for the OpenCL language are:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -195,6 +195,10 @@
 - ``-dumpdir`` has been implemented to specify auxiliary and dump output
   filenames for features like ``-gsplit-dwarf``.
 
+- The flag ``-std=c++2c`` has been added. This compiles C++ code using the
+  Working Draft for ISO C++ 2026.
+
+
 Deprecated Compiler Flags
 -------------------------
 
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -98,6 +98,7 @@
 LANGOPT(CPlusPlus17       , 1, 0, "C++17")
 LANGOPT(CPlusPlus20       , 1, 0, "C++20")
 LANGOPT(CPlusPlus23       , 1, 0, "C++23")
+LANGOPT(CPlusPlus26       , 1, 0, "C++26")
 LANGOPT(ObjC              , 1, 0, "Objective-C")
 BENIGN_LANGOPT(ObjCDefaultSynthProperties , 1, 0,
                "Objective-C auto-synthesized properties")
diff --git a/clang/include/clang/Basic/LangStandard.h b/clang/include/clang/Basic/LangStandard.h
--- a/clang/include/clang/Basic/LangStandard.h
+++ b/clang/include/clang/Basic/LangStandard.h
@@ -56,11 +56,12 @@
   CPlusPlus17 = (1 << 8),
   CPlusPlus20 = (1 << 9),
   CPlusPlus23 = (1 << 10),
-  Digraphs = (1 << 11),
-  GNUMode = (1 << 12),
-  HexFloat = (1 << 13),
-  OpenCL = (1 << 14),
-  HLSL = (1 << 15)
+  CPlusPlus26 = (1 << 11),
+  Digraphs = (1 << 12),
+  GNUMode = (1 << 13),
+  HexFloat = (1 << 14),
+  OpenCL = (1 << 15),
+  HLSL = (1 << 16)
 };
 
 /// LangStandard - Information about the properties of a particular language
@@ -121,6 +122,9 @@
   /// isCPlusPlus23 - Language is a post-C++23 variant (or later).
   bool isCPlusPlus23() const { return Flags & CPlusPlus23; }
 
+  /// isCPlusPlus26 - Language is a post-C++23 variant (or later).
+  bool isCPlusPlus26() const { return Flags & CPlusPlus26; }
+
   /// hasDigraphs - Language supports digraphs.
   bool hasDigraphs() const { return Flags & Digraphs; }
 
diff --git a/clang/include/clang/Basic/LangStandards.def b/clang/include/clang/Basic/LangStandards.def
--- a/clang/include/clang/Basic/LangStandards.def
+++ b/clang/include/clang/Basic/LangStandards.def
@@ -163,6 +163,18 @@
              CPlusPlus20 | CPlusPlus23 | Digraphs | HexFloat | GNUMode)
 LANGSTANDARD_ALIAS_DEPR(gnucxx23, "gnu++2b")
 
+LANGSTANDARD(cxx26, "c++26",
+             CXX, "Working draft for ISO C++ 2026 DIS",
+             LineComment | CPlusPlus | CPlusPlus11 | CPlusPlus14 | CPlusPlus17 |
+             CPlusPlus20 | CPlusPlus23 | CPlusPlus26 | Digraphs | HexFloat)
+LANGSTANDARD_ALIAS_DEPR(cxx26, "c++2c")
+
+LANGSTANDARD(gnucxx26, "gnu++26",
+             CXX, "Working draft for ISO C++ 2026 DIS with GNU extensions",
+             LineComment | CPlusPlus | CPlusPlus11 | CPlusPlus14 | CPlusPlus17 |
+             CPlusPlus20 | CPlusPlus23 | CPlusPlus26 | Digraphs | HexFloat | GNUMode)
+LANGSTANDARD_ALIAS_DEPR(gnucxx26, "gnu++2c")
+
 // OpenCL
 LANGSTANDARD(opencl10, "cl1.0",
              OpenCL, "OpenCL 1.0",
diff --git a/clang/lib/Basic/LangOptions.cpp b/clang/lib/Basic/LangOptions.cpp
--- a/clang/lib/Basic/LangOptions.cpp
+++ b/clang/lib/Basic/LangOptions.cpp
@@ -118,6 +118,7 @@
   Opts.CPlusPlus17 = Std.isCPlusPlus17();
   Opts.CPlusPlus20 = Std.isCPlusPlus20();
   Opts.CPlusPlus23 = Std.isCPlusPlus23();
+  Opts.CPlusPlus26 = Std.isCPlusPlus26();
   Opts.GNUMode = Std.isGNUMode();
   Opts.GNUCVersion = 0;
   Opts.HexFloats = Std.hasHexFloats();
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -1397,6 +1397,7 @@
       !Args.hasArg(options::OPT_fmodules) && Std &&
       (Std->containsValue("c++20") || Std->containsValue("c++2a") ||
        Std->containsValue("c++23") || Std->containsValue("c++2b") ||
+       Std->containsValue("c++26") || Std->containsValue("c++2c") ||
        Std->containsValue("c++latest"));
 
   // Process -fmodule-header{=} flags.
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3674,6 +3674,7 @@
       IsCXX && Std &&
       (Std->containsValue("c++2a") || Std->containsValue("c++20") ||
        Std->containsValue("c++2b") || Std->containsValue("c++23") ||
+       Std->containsValue("c++2c") || Std->containsValue("c++26") ||
        Std->containsValue("c++latest"));
   bool HaveModules = HaveStdCXXModules;
 
@@ -6646,7 +6647,7 @@
                              .Case("c++17", "-std=c++17")
                              .Case("c++20", "-std=c++20")
                              // TODO add c++23 when MSVC supports it.
-                             .Case("c++latest", "-std=c++23")
+                             .Case("c++latest", "-std=c++26")
                              .Default("");
       if (LanguageStandard.empty())
         D.Diag(clang::diag::warn_drv_unused_argument)
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -451,8 +451,11 @@
       Builder.defineMacro("__STDC_VERSION__", "199409L");
   } else {
     //   -- __cplusplus
+    // FIXME: Use correct value for C++26.
+    if (LangOpts.CPlusPlus26)
+      Builder.defineMacro("__cplusplus", "202401L");
     // FIXME: Use correct value for C++23.
-    if (LangOpts.CPlusPlus23)
+    else if (LangOpts.CPlusPlus23)
       Builder.defineMacro("__cplusplus", "202101L");
     //      [C++20] The integer literal 202002L.
     else if (LangOpts.CPlusPlus20)
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -604,7 +604,7 @@
 // STDCXX20: -std=c++20
 
 // RUN: %clang_cl -fmsc-version=1900 -TP -std:c++latest -### -- %s 2>&1 | FileCheck -check-prefix=STDCXXLATEST %s
-// STDCXXLATEST: -std=c++23
+// STDCXXLATEST: -std=c++26
 
 // RUN: env CL="/Gy" %clang_cl -### -- %s 2>&1 | FileCheck -check-prefix=ENV-CL %s
 // ENV-CL: "-ffunction-sections"
diff --git a/clang/test/Driver/unknown-std.cpp b/clang/test/Driver/unknown-std.cpp
--- a/clang/test/Driver/unknown-std.cpp
+++ b/clang/test/Driver/unknown-std.cpp
@@ -19,6 +19,8 @@
 // CHECK-NEXT: note: use 'gnu++20' for 'ISO C++ 2020 DIS with GNU extensions' standard
 // CHECK-NEXT: note: use 'c++23' for 'ISO C++ 2023 DIS' standard
 // CHECK-NEXT: note: use 'gnu++23' for 'ISO C++ 2023 DIS with GNU extensions' standard
+// CHECK-NEXT: note: use 'c++26' for 'Working draft for ISO C++ 2026 DIS' standard
+// CHECK-NEXT: note: use 'gnu++26' for 'Working draft for ISO C++ 2026 DIS with GNU extensions' standard
 // CUDA-NEXT: note: use 'cuda' for 'NVIDIA CUDA(tm)' standard
 
 // Make sure that no other output is present.
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -9,6 +9,16 @@
 // BLOCKS:#define __block __attribute__((__blocks__(byref)))
 //
 //
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++26 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2C %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++2c -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2C %s
+//
+// CXX2C:#define __GNUG__ 4
+// CXX2C:#define __GXX_EXPERIMENTAL_CXX0X__ 1
+// CXX2C:#define __GXX_RTTI 1
+// CXX2C:#define __GXX_WEAK__ 1
+// CXX2C:#define __cplusplus 202401L
+// CXX2C:#define __private_extern__ extern
+//
 // RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++23 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2B %s
 //
 // CXX2B:#define __GNUG__ 4
@@ -133,6 +143,14 @@
 // RUN: %clang_cc1 -ffreestanding -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix FREESTANDING %s
 // FREESTANDING:#define __STDC_HOSTED__ 0
 //
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++26 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2C %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++2c -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2C %s
+//
+// GXX2C:#define __GNUG__ 4
+// GXX2C:#define __GXX_WEAK__ 1
+// GXX2C:#define __cplusplus 202401L
+// GXX2C:#define __private_extern__ extern
+//
 // RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++23 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2B %s
 //
 // GXX2B:#define __GNUG__ 4