German submarine U-923 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. She was ordered on 6 June 1941, and was laid down on 21 February 1942 at Neptun Werft AG, Rostock, as yard number 510. She was launched on 7 August 1943 and commissioned under the command of Leutnant zur See Heinz Frömmer on 4 October 1943.