diff --git a/clang/lib/Basic/Targets/AVR.cpp b/clang/lib/Basic/Targets/AVR.cpp
--- a/clang/lib/Basic/Targets/AVR.cpp
+++ b/clang/lib/Basic/Targets/AVR.cpp
@@ -300,6 +300,7 @@
   Builder.defineMacro("AVR");
   Builder.defineMacro("__AVR");
   Builder.defineMacro("__AVR__");
+  Builder.defineMacro("__ELF__");
 
   if (!this->CPU.empty()) {
     auto It = llvm::find_if(
diff --git a/clang/test/CodeGen/avr/target-cpu-defines/atmega328p.c b/clang/test/CodeGen/avr/target-cpu-defines/atmega328p.c
--- a/clang/test/CodeGen/avr/target-cpu-defines/atmega328p.c
+++ b/clang/test/CodeGen/avr/target-cpu-defines/atmega328p.c
@@ -5,3 +5,4 @@
 // CHECK: #define __AVR 1
 // CHECK: #define __AVR_ATmega328P__ 1
 // CHECK: #define __AVR__ 1
+// CHECK: #define __ELF__ 1
diff --git a/clang/test/CodeGen/avr/target-cpu-defines/attiny104.c b/clang/test/CodeGen/avr/target-cpu-defines/attiny104.c
--- a/clang/test/CodeGen/avr/target-cpu-defines/attiny104.c
+++ b/clang/test/CodeGen/avr/target-cpu-defines/attiny104.c
@@ -5,3 +5,4 @@
 // CHECK: #define __AVR 1
 // CHECK: #define __AVR_ATtiny104__ 1
 // CHECK: #define __AVR__ 1
+// CHECK: #define __ELF__ 1
diff --git a/clang/test/CodeGen/avr/target-cpu-defines/common.c b/clang/test/CodeGen/avr/target-cpu-defines/common.c
--- a/clang/test/CodeGen/avr/target-cpu-defines/common.c
+++ b/clang/test/CodeGen/avr/target-cpu-defines/common.c
@@ -4,3 +4,4 @@
 // CHECK: #define AVR 1
 // CHECK: #define __AVR 1
 // CHECK: #define __AVR__ 1
+// CHECK: #define __ELF__ 1