SM U-87[Note 1] was one of the 329 submarines serving in the Imperial German Navy (Kaiserliche Marine) in World War I. U-87 was engaged in the naval warfare and took part in the First Battle of the Atlantic.

[4] She sank some 22 merchant vessels before 25 December 1917, when HMS Buttercup rammed U-87 in the Irish Sea and depth-charged her.

U-87 was fitted with four 50 centimetres (20 in) torpedo tubes (two at the bow and two at the stern), ten to twelve torpedoes, one 10.5 cm (4.1 in) SK L/45 deck gun, and one 8.8 cm (3.5 in) SK L/30 deck gun.

[1] In August 2017, researchers from Bangor University in Wales announced they had discovered the sunken wreck of U-87 while conducting multibeam surveys 10 miles northwest of Bardsey Island as part of the marine renewable energy SEACAMS 2 project.

[6][7] Detailed sonar images reveal the wreck to be lying in one piece with what appears to be a large area of damage near the conning tower, presumably caused by in the ramming collision by escort P.56.