HMS L55 was a British L class submarine built by Fairfield Shipbuilding and Engineering Company, Govan, Clyde.

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.

On 9 June 1919 in Caporsky Bay in the Gulf of Finland L55 attacked two 1,260-ton Bolshevik Orfey-class minelayer-destroyers, Gavriil and Azard.

[4] The crew, 42 officers and men, were buried in a communal grave at the Haslar Royal Naval Cemetery in Portsmouth on 7 September 1928.

[5][6] 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".