Unterseeboot 553 (U-553) was a Type VIIC submarine of the Kriegsmarine. Her keel was laid down 21 November 1939, by Blohm + Voss of Hamburg. She was commissioned 23 December 1940, with Kapitänleutnant Karl Thurmann in command. Thurmann commanded her for her entire career.

U-553 conducted ten patrols, sinking 13 ships totalling 64,612 tons and damaging two others totalling 15,273 tons.

On 25 April 1941 major engine trouble forced U-553 to return to base.

On 20 January 1943, U-553 sent a radio message: "sehrohr unklar" (periscope not clear), and was never heard from again. She had suffered no casualties to her crew until lost with all hands.

Neal Stephenson's novel Cryptonomicon includes a fictitious U-553 which runs aground in a fictional location near the northern British Isles. It is possible that Stephenson picked the number of the boat not for historical accuracy but rather as the product of two primes, 7 and 79.

See also: List of U-boats