German submarine U-73 was a Type VIIB U-boat of the Kriegsmarine (German Navy) during World War II. She was laid down by Bremer Vulkan of Bremen-Vegesack, Germany as 'Werk' 1 on 5 November 1939, launched on 27 July 1940 and commissioned on 30 September of the same year under Kapitänleutnant (Kptlt.) Helmut Rosenbaum.