diff --git a/lld/MachO/Options.td b/lld/MachO/Options.td
--- a/lld/MachO/Options.td
+++ b/lld/MachO/Options.td
@@ -701,6 +701,11 @@
 def fatal_warnings : Flag<["-"], "fatal_warnings">,
     HelpText<"Treat warnings as errors">,
     Group<grp_rare>;
+def _fatal_warnings : Flag<["-"], "fatal-warnings">,
+    Alias<fatal_warnings>,
+    HelpText<"Alias for -fatal_warnings to match other platforms">,
+    Flags<[HelpHidden]>,
+    Group<grp_rare>;
 def no_eh_labels : Flag<["-"], "no_eh_labels">,
     HelpText<"In -r mode, suppress .eh labels in the __eh_frame section">,
     Flags<[HelpHidden]>,
diff --git a/lld/test/MachO/fatal-warnings.s b/lld/test/MachO/fatal-warnings.s
--- a/lld/test/MachO/fatal-warnings.s
+++ b/lld/test/MachO/fatal-warnings.s
@@ -3,8 +3,12 @@
 
 # RUN: %no_fatal_warnings_lld %t1.o -o /dev/null -single_module 2>&1 \
 # RUN:     | FileCheck -check-prefix=WARNING %s
+# RUN: %no_fatal_warnings_lld %t1.o -o /dev/null -fatal_warnings
+# RUN: %no_fatal_warnings_lld %t1.o -o /dev/null -fatal-warnings
 # RUN: not %no_fatal_warnings_lld %t1.o -fatal_warnings -o /dev/null \
 # RUN:     -single_module 2>&1 | FileCheck -check-prefix=ERROR %s
+# RUN: not %no_fatal_warnings_lld %t1.o -fatal-warnings -o /dev/null \
+# RUN:     -single_module 2>&1 | FileCheck -check-prefix=ERROR %s
 
 # ERROR: error: Option `-single_module' is deprecated
 # WARNING: warning: Option `-single_module' is deprecated