SM UB-61 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 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 and sunk with all hands lost.
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 deck gun. UB-61 would carry a crew of up to 3 officer and 31 men and had a cruising range of . UB-61 had a displacement of while surfaced and when submerged. Her engines enabled her to travel at when surfaced and when submerged.