German submarine U-621

German submarine U-621 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 1 July 1941 by Blohm & Voss in Hamburg as 'werk' 597, launched on 19 March 1942 and commissioned on 7 May 1942 under Kapitänleutnant Horst Schünemann.

Service History
The boat's service began on 7 May 1942 for training as part of the 8th U-boat Flotilla. After training was completed she transferred to the 9th flotilla on 1 October 1942 for active service.

In 10 patrols she sank 4 merchant ships for a total of 20,159 GRT, plus 1 auxiliary warship. She also damaged 2 ships.

Wolf Packs
She took part in 11 wolfpacks, namely,
 * Panther (10 Oct 1942 – 16 Oct 1942)
 * Puma (16 Oct 1942 – 29 Oct 1942)
 * Raufbold (11 Dec 1942 – 18 Dec 1942)
 * Hartherz (3 Feb 1943 – 7 Feb 1943)
 * Ritter (11 Feb 1943 – 26 Feb 1943)
 * Burggraf (4 Mar 1943 – 5 Mar 1942)
 * Raubgraf (7 Mar 1943 – 15 Mar 1943)
 * Amsel 1 (3 May 1943 – 6 May 1943)
 * Elbe (7 May 1943 – 10 May 1943)
 * Elbe 2 (10 May 1943 – 14 May 1943)
 * Mosel (19 May 1943 – 24 May 1943)

Fate
She was sunk by a depth charges dropped by three Royal Canadian Navy destroyers, HMCS Ottawa (H31), HMCS Kootenay (H75) and HMCS Chaudiere (H99) on 18 August 1944 near La Rochelle at position 45.86667°N, -2.6°W.