diff --git a/core/config.mk b/core/config.mk
index c8a0edca6..a349d16bb 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -192,6 +192,15 @@ include $(BUILD_SYSTEM)/envsetup.mk
 # See envsetup.mk for a description of SCAN_EXCLUDE_DIRS
 FIND_LEAVES_EXCLUDES := $(addprefix --prune=, $(OUT_DIR) $(SCAN_EXCLUDE_DIRS) .repo .git)
 
+ifdef BRILLO
+# Add a C define that identifies Brillo targets. __BRILLO__ should only be used
+# to differentiate between Brillo and non-Brillo-but-Android environments. Use
+# __ANDROID__ instead to test if something is being built in an Android-derived
+# environment (including Brillo) as opposed to an entirely different
+# environment (e.g. Chrome OS).
+COMMON_GLOBAL_CFLAGS += -D__BRILLO__
+endif
+
 # ---------------------------------------------------------------
 # We run gcc/clang with PWD=/proc/self/cwd to remove the $TOP
 # from the debug output. That way two builds in two different