SM UB-25 was a German Type UB II submarine or U-boat in the German Imperial Navy () during World War I. The U-boat was ordered on 30 April 1915 and launched on 9 October 1915. She was commissioned into the German Imperial Navy on 11 December 1915 as SM UB-25. The submarine was lost in a collision with SMS V26 in Kiel harbour on 17 March 1917. She was raised on 22 March 1917 by the salvage ship SMS Vulcan and served on as a training boat until she was surrendered to Britain in accordance with the requirements of the Armistice with Germany on 26 November 1918. UB-25 was finally broken up in Canning Town in 1922.