Index: clang-tidy/misc/DefinitionsInHeadersCheck.cpp
===================================================================
--- clang-tidy/misc/DefinitionsInHeadersCheck.cpp
+++ clang-tidy/misc/DefinitionsInHeadersCheck.cpp
@@ -139,6 +139,9 @@
     // Ignore variable definition within function scope.
     if (VD->hasLocalStorage() || VD->isStaticLocal())
       return;
+    // Ignore inline variables.
+    if (VD->isInline())
+      return;
 
     diag(VD->getLocation(),
          "variable %0 defined in a header file; "
Index: docs/clang-tidy/checks/misc-definitions-in-headers.rst
===================================================================
--- docs/clang-tidy/checks/misc-definitions-in-headers.rst
+++ docs/clang-tidy/checks/misc-definitions-in-headers.rst
@@ -74,6 +74,14 @@
    template <typename T>
    void B<T>::f1() {}
 
+   class CE {
+     constexpr static int i = 5; // OK: inline variable definition.
+   };
+
+   inline int i = 5; // OK: inline variable definition.
+
+   constexpr int k = 1; // OK: constexpr variable has internal linkage.
+
 Options
 -------
 
Index: test/clang-tidy/misc-definitions-in-headers-1z.hpp
===================================================================
--- /dev/null
+++ test/clang-tidy/misc-definitions-in-headers-1z.hpp
@@ -0,0 +1,10 @@
+// RUN: %check_clang_tidy %s misc-definitions-in-headers %t -- -- -std=c++1z
+
+class CE {
+  constexpr static int i = 5; // OK: inline variable definition.
+};
+
+inline int i = 5; // OK: inline variable definition.
+
+int b = 1;
+// CHECK-MESSAGES: :[[@LINE-1]]:5: warning: variable 'b' defined in a header file; variable definitions in header files can lead to ODR violations [misc-definitions-in-headers]
Index: test/clang-tidy/misc-definitions-in-headers.hpp
===================================================================
--- test/clang-tidy/misc-definitions-in-headers.hpp
+++ test/clang-tidy/misc-definitions-in-headers.hpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s misc-definitions-in-headers %t
+// RUN: %check_clang_tidy %s misc-definitions-in-headers %t -- -- -std=c++11
 
 int f() {
 // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'f' defined in a header file; function definitions in header files can lead to ODR violations [misc-definitions-in-headers]
@@ -175,3 +175,5 @@
 int CD<T, int>::f() { // OK: partial template specialization.
   return 0;
 }
+
+constexpr int k = 1; // OK: constexpr variable has internal linkage.