German submarine U-540 was a Type IXC U-boat of the Nazi German Kriegsmarine during World War II. She was laid down at the Deutsche Werft (yard) in Hamburg as 'werk' 361 on 12 May 1942, launched on 18 December and commissioned on 10 March 1943 with Kapitänleutnant Lorenz Kasch in command. U-540 began her service career with training as part of the 4th U-boat Flotilla from 10 March 1943. She was re-assigned to the 10th flotilla for operations on 1 October. She carried out one patrol and did not sink any ships. She was a member of one wolfpack.