diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -452,6 +452,8 @@
     switch (os) {
     case llvm::Triple::Linux:
       return new LinuxTargetInfo<SystemZTargetInfo>(Triple, Opts);
+    case llvm::Triple::ZOS:
+      return new ZOSTargetInfo<SystemZTargetInfo>(Triple, Opts);
     default:
       return new SystemZTargetInfo(Triple, Opts);
     }
diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -728,6 +728,55 @@
   bool defaultsToAIXPowerAlignment() const override { return true; }
 };
 
+// z/OS target
+template <typename Target>
+class LLVM_LIBRARY_VISIBILITY ZOSTargetInfo : public OSTargetInfo<Target> {
+protected:
+  void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
+                    MacroBuilder &Builder) const override {
+    // FIXME: _LONG_LONG should not be defined under -std=c89.
+    Builder.defineMacro("_LONG_LONG");
+    Builder.defineMacro("_OPEN_DEFAULT");
+    // _UNIX03_WITHDRAWN is required to build libcxx.
+    Builder.defineMacro("_UNIX03_WITHDRAWN");
+    Builder.defineMacro("__370__");
+    Builder.defineMacro("__BFP__");
+    // FIXME: __BOOL__ should not be defined under -std=c89.
+    Builder.defineMacro("__BOOL__");
+    Builder.defineMacro("__LONGNAME__");
+    Builder.defineMacro("__MVS__");
+    Builder.defineMacro("__THW_370__");
+    Builder.defineMacro("__THW_BIG_ENDIAN__");
+    Builder.defineMacro("__TOS_390__");
+    Builder.defineMacro("__TOS_MVS__");
+    Builder.defineMacro("__XPLINK__");
+
+    if (this->PointerWidth == 64)
+      Builder.defineMacro("__64BIT__");
+
+    if (Opts.CPlusPlus) {
+      Builder.defineMacro("__DLL__");
+      // _XOPEN_SOURCE=600 is required to build libcxx.
+      Builder.defineMacro("_XOPEN_SOURCE", "600");
+    }
+
+    if (Opts.GNUMode) {
+      Builder.defineMacro("_MI_BUILTIN");
+      Builder.defineMacro("_EXT");
+    }
+
+    if (Opts.CPlusPlus && Opts.WChar) {
+      // Macro __wchar_t is defined so that the wchar_t data
+      // type is not declared as a typedef in system headers.
+      Builder.defineMacro("__wchar_t");
+    }
+  }
+
+public:
+  ZOSTargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
+      : OSTargetInfo<Target>(Triple, Opts) {}
+};
+
 void addWindowsDefines(const llvm::Triple &Triple, const LangOptions &Opts,
                        MacroBuilder &Builder);
 
diff --git a/clang/test/Preprocessor/init-zos.c b/clang/test/Preprocessor/init-zos.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Preprocessor/init-zos.c
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -E -dM -ffreestanding -triple=s390x-none-zos -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix S390X-ZOS %s
+// RUN: %clang_cc1 -x c++ -std=gnu++14 -E -dM -ffreestanding -triple=s390x-none-zos -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix S390X-ZOS -check-prefix S390X-ZOS-GNUXX %s
+
+// S390X-ZOS-GNUXX:#define _EXT 1
+// S390X-ZOS:#define _LONG_LONG 1
+// S390X-ZOS-GNUXX:#define _MI_BUILTIN 1
+// S390X-ZOS:#define _OPEN_DEFAULT 1
+// S390X-ZOS:#define _UNIX03_WITHDRAWN 1
+// S390X-ZOS-GNUXX:#define _XOPEN_SOURCE 600
+// S390X-ZOS:#define __370__ 1
+// S390X-ZOS:#define __64BIT__ 1
+// S390X-ZOS:#define __BFP__ 1
+// S390X-ZOS:#define __BOOL__ 1
+// S390X-ZOS-GNUXX:#define __DLL__ 1
+// S390X-ZOS:#define __LONGNAME__ 1
+// S390X-ZOS:#define __MVS__ 1
+// S390X-ZOS:#define __THW_370__ 1
+// S390X-ZOS:#define __THW_BIG_ENDIAN__ 1
+// S390X-ZOS:#define __TOS_390__ 1
+// S390X-ZOS:#define __TOS_MVS__ 1
+// S390X-ZOS:#define __XPLINK__ 1
+// S390X-ZOS-GNUXX:#define __wchar_t 1