|Builder:||Fairfield Shipbuilding and Engineering Company, Govan|
|Launched:||29 September 1918|
|Fate:||Sunk, 9 June 1919|
|Acquired:||Raised, 11 August 1928, and repaired|
|Recommissioned:||7 August 1931|
|Renamed:||7 August 1931|
|Fate:||Scrapped c. 1960|
|Class and type:||L class submarine|
|Length:||230 ft 6 in (70.26 m)|
|Beam:||23 ft 6 in (7.16 m)|
|Draught:||13 ft 1 in (3.99 m)|
|Range:||4,500 nmi (8,300 km) at 8 kn (15 km/h; 9.2 mph)|
In 1919 L55 was sunk in the Baltic Sea by Bolshevik vessels while serving as part of the Allied intervention in the Russian Civil War. The submarine was raised in 1928 and repaired by the Soviets. After being used for training, she finally was scrapped in the 1950s.
HMS L55 was based at Tallinn, Estonia as part of the Baltic Battle Squadron which was supporting the Baltic states fighting for independence. On 9 June 1919 in Caporsky Bay in the Gulf of Finland L55 attacked two 1,260-ton Bolshevik Orfey-class minelayer-destroyers, Gavril and Azard. HMS L55 missed her targets and was forced into a British-laid minefield. Soviet sources stated Azard sank her by gunfire. If she was sunk by gunfire, L55 was the only British submarine sunk by hostile Soviet vessels.
The wreck was found by Soviet minesweepers in 1927. The Soviets raised her on 11 August 1928. As the Soviets refused to allow any British warship into their waters, the remains of 34 crew members were returned on the British merchantman Truro before transfer to HMS Champion. The crew was buried in a communal grave at Haslar Royal Naval Cemetery in Portsmouth on 7 September 1928.
The boat was rebuilt by Baltic Works, Leningrad, the reconstruction cost of 1 million roubles being financed by a public fund as "an answer to Chamberlain". She was recommissioned as a Soviet submarine with the same number (Л-55) on 7 August 1931. She was later named Bezbozhnik ("Atheist") and was used as the basis of design for the Soviet L-class submarines. L55 was used for training until the beginning of World War II, when she was damaged in an accident in early 1941. She was scrapped in 1953 or possibly 1960.