SM UB-120 was a German Type UB III submarine or U-boat in the German Imperial Navy () during World War I. She was commissioned into the German Imperial Navy on 23 March 1918 as SM UB-120. UB-120 was surrendered to the British on 24 November 1918 in accordance with the requirements of the Armistice with Germany. She was broken up in Swansea in 1922