German submarine U-903 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. She was ordered on 16 July 1942, and was laid down on 25 August 1942 at Flender Werke AG, Lübeck, as yard number 329. She was launched on 17 July 1943 and commissioned under the command of Leutnant zur See Hans Hellmann on 4 September 1943.