German submarine U-54 was a Type VIIB U-boat of Nazi Germany's Kriegsmarine during World War II.
German Type VIIB submarines were preceded by the shorter Type VIIA submarines. U-54 had a displacement of when at the surface and while submerged. She had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two MAN M 6 V 40/46 four-stroke, six-cylinder supercharged diesel engines producing a total of for use while surfaced, two BBC GG UB 720/8 double-acting electric motors producing a total of for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-54 was fitted with five torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one SK C/35 naval gun, 220 rounds, and one anti-aircraft gun The boat had a complement of between forty-four and sixty.
She was ordered on 16 July 1937 and was laid down on 13 September 1938 at Friedrich Krupp Germaniawerft, Kiel, becoming yard number 589. She was launched on 15 August 1939 and commissioned under her first commander, Kapitänleutnant (Kptlt.) Georg-Heinz Michel, on 23 September of that year. Michel commanded her for her work-ups with the 7th U-boat Flotilla between 23 September and 30 November 1939. He was succeeded by Korvettenkapitän (K.Kapt.) Günter Kutschmann on 5 December, who completed the training programme by 31 December. She became an operational boat of the 7th Flotilla and set out for her first and only war patrol on 1 January 1940 in the North Sea. She did not record any successes during this cruise and was reported missing after failing to check in on 20 February.
She was probably lost with all hands after striking a mine in the mine barrages Field No. 4 or Field No. 6, which had been laid by the Royal Navy destroyers and in early January 1940. This however has not been proven and the reason for her disappearance remains officially unknown. Part of one of her torpedoes was found on 14 March 1940 by the German patrol boat in position .