German submarine U-503

German submarine U-503 was a Type IXC U-boat of the Nazi German Kriegsmarine during World War II. The submarine was laid down on 29 April 1940 at the Deutsche Werft yard in Hamburg as 'werk' 293, launched on 5 April 1941 and commissioned on 10 July 1941 under the command of Kapitänleutnant Otto Gericke.

The boat's service began with her being assigned to the 2nd U-boat Flotilla on her commissioning date for training and continuing with it for operations from 1 February 1942.

Service history
U-503's first and only active war patrol began at Bergen in Norway on 28 February 1942, following two previous port to port sailings. The U-boat was sunk on 15 March by depth charges dropped by a PBO-1 Hudson of United States Navy squadron VP-82 south-east of Newfoundland, in position 45.83333°N, -48.83333°W.

The aircraft, from Argentia, was escorting Convoy ON-72. The PBO-1s were twenty Hudson Mk.IIIA aircraft diverted from Lend-Lease to equip VP-82, and sank the first two U-boats by US forces; GS U-656 on 1 March 1942 and U-503.