German submarine U-66 was a Type IXC U-boat of the German Kriegsmarine during World War II. The submarine was laid down on 20 March 1940 at the AG Weser yard at Bremen, launched on 10 October and commissioned on 2 January 1941 under the command of Kapitänleutnant Richard Zapp as part of the 2. Unterseebootsflottille. After her transfer from a training organization to front line service in May 1941, until her sinking in May 1944, U-66 conducted nine combat patrols, sinking 33 merchant ships, for a total of , and damaged two British motor torpedo boats. She was a member of four wolfpacks.