German submarine U-186 was a Type IXC/40 U-boat of the Nazi German Kriegsmarine built for service during World War II. Her keel was laid down on 24 July 1941 by AG Weser in Bremen as 'werk' 1026. She was launched on 11 March 1942 and commissioned on 10 July with Korvettenkapitän Siegfried Hesemann in command. The U-boat's service began with training as part of the 4th U-boat Flotilla. She then moved to the 10th flotilla on 1 January 1943 for operations. The submarine carried out two patrols and was a member of nine wolf packs. She sank three ships totalling .