SM UB-61 was a German Type UB III submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. She was commissioned into the German Imperial Navy on 23 June 1917 as SM UB-61.
The submarine conducted three patrols and sank two ships during the war for a total loss of . UB-61 was struck by a mine on 29 November 1917 at 53.3333°N 60°W and sunk with all hands lost.
See main article: Type UB III submarine. UB-61 was ordered by the GIN on 20 May 1916.
She was built by AG Vulcan of Hamburg and following just under a year of construction, launched at Hamburg on 28 April 1917. UB-61 was commissioned later that same year . Like all Type UB III submarines, UB-61 carried 10 torpedoes and was armed with a 8.82NaN2 deck gun. UB-61 would carry a crew of up to 3 officer and 31 men and had a cruising range of 8420nmi. UB-61 had a displacement of 508lk=inNaNlk=in while surfaced and 639t when submerged. Her engines enabled her to travel at 13.3kn when surfaced and when submerged.
| Date | Name | Nationality | Tonnage[1] | Fate[2] | |
|---|---|---|---|---|---|
| 25 August 1917 | Sycamore |  United Kingdom | 6,550 | Sunk | |
| 26 August 1917 | Assyria | United Kingdom | 6,370 | Sunk |