diff --git a/lld/ELF/Config.h b/lld/ELF/Config.h
index 00de985c0d5e..612ad8fa3475 100644
--- a/lld/ELF/Config.h
+++ b/lld/ELF/Config.h
@@ -66,6 +66,7 @@ struct Configuration {
   ELFKind EKind = ELFNoneKind;
   uint16_t EMachine = llvm::ELF::EM_NONE;
   uint64_t EntryAddr = -1;
+  unsigned Optimize = 0;
 };
 
 extern Configuration *Config;
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index acb9d9b36d43..ee74722d5b73 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -156,6 +156,12 @@ void LinkerDriver::createFiles(opt::InputArgList &Args) {
   Config->SoName = getString(Args, OPT_soname);
   Config->Sysroot = getString(Args, OPT_sysroot);
 
+  if (auto *Arg = Args.getLastArg(OPT_O)) {
+    StringRef Val = Arg->getValue();
+    if (Val.getAsInteger(10, Config->Optimize))
+      error("Invalid optimization level");
+  }
+
   if (auto *Arg = Args.getLastArg(OPT_hash_style)) {
     StringRef S = Arg->getValue();
     if (S == "gnu") {
diff --git a/lld/ELF/Options.td b/lld/ELF/Options.td
index 219547248075..3bf076eb8082 100644
--- a/lld/ELF/Options.td
+++ b/lld/ELF/Options.td
@@ -12,6 +12,8 @@ def Bstatic: Flag<["-"], "Bstatic">,
 def L : Joined<["-"], "L">, MetaVarName<"<dir>">,
   HelpText<"Directory to search for libraries">;
 
+def O : Joined<["-"], "O">, HelpText<"Optimize">;
+
 def allow_multiple_definition: Flag<["--"], "allow-multiple-definition">,
   HelpText<"Allow multiple definitions">;
 
@@ -125,7 +127,6 @@ def alias_script_T : Separate<["-"], "T">, Alias<script>;
 def alias_undefined_u : Separate<["-"], "u">, Alias<undefined>;
 
 // Options listed below are silently ignored now.
-def O3 : Flag<["-"], "O3">;
 def build_id : Flag<["--"], "build-id">;
 def eh_frame_hdr : Flag<["--"], "eh-frame-hdr">;
 def end_group : Flag<["--"], "end-group">;