SM U-120 was a Type UE II long-range minelayer submarine of the Imperial German Navy.[1] 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.
Type UE II submarines were preceded by the shorter Type UE I submarines. U-120 had a displacement of 1164t when at the surface and 1512t while submerged. She had a total length of 81.52m (267.45feet), a beam of 7.42m (24.34feet), a height of 10.16m (33.33feet), and a draught of 4.22m (13.85feet). The submarine was powered by two 2400PS engines for use while surfaced, and two 1200PS engines for use while submerged. She had two shafts and two 1.61m (05.28feet) propellers. She was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, she could operate for at ; when surfaced, she could travel at . U-120 was fitted with four torpedo tubes (fitted at its bow), fourteen torpedoes, two mine chutes (fitted at its stern), forty-two mines, one 15sp=usNaNsp=us SK L/45 deck gun, and 494 rounds. She had a complement of forty (thirty-six crew members and four officers).