SM U-120 was a Type UE II long-range minelayer submarine of the Imperial German Navy. She was built at Hamburg, Germany, by Aktiengesellschaft Vulcan and launched on 20 June 1918. She was commissioned in the Imperial German Navy on 31 August 1918 with Kapitänleutnant Hans von Mellenthin in command. She had a short-lived career, not being assigned to any flotillas, nor achieving any successful attacks on enemy shipping, before the end of the First World War. She was surrendered to Italy on 22 November 1918, and was broken up in April 1919 at La Spezia.