U-109 was a submarine in the Imperial German Navy in World War I, taking part in the First Battle of the Atlantic. The building contract was confirmed 5 May 1916, and was awarded to Germaniawerft, Kiel. A Type 93 boat, she was launched 25 September 1917 and commissioned 7 November. She was under the command of Otto Ney. On 28 January 1918, she was sunk in the English Channel, possibly by a mine, while diving to avoid ships from the Dover Patrol (particularly drifter H.M. Beryl III). She sank no ships.