German submarine U-640

German submarine U-640 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 30 October 1941 by Blohm & Voss, Hamburg as yard number 616, launched on 23 July 1942 and commissioned on 17 September 1942 under Oberleutnant zur See Karl-Heinz Nagel.

Service History
The boat's career began with training at 5th U-boat Flotilla on 17 September 1942, followed by active service on 1 May 1943 as part of the 6th Flotilla.

In 1 patrol she sank no ships.

Wolfpacks
U-640 took part in one wolfpack, namely
 * Iller (12–14 May 1943)

Fate
There are discrepancies between the fate of U-640 and GS U-657, which was sunk in the same vicinity around the same time. Paul Kemp’s book attributes the sinking of British freighter Aymeric to U-640, and then subsequently sunk by HMS Swale (K217) on the 17 May 1943, whereas UBoat.net attributes this success and fate to U-657.

Uboat.net states that U-640 was sunk on 14 May 1943 in the Atlantic Ocean in position 60.53333°N, -31.08333°W, by depth charges from a US Catalina of VP-84 Squadron. All hands were lost.