German submarine U-666

German submarine U-666 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 16 September 1941 by Deutsche Werft, Hamburg as yard number 815, launched on 18 July 1942 and commissioned on 26 August 1942 under Kapitänleutnant Herbert Engel. Oberleutnant zur See Ernst Wilberg took over command on 10 December 1943.

Service History
The boat's career began with training at 5th U-boat Flotilla on 26 August 1942, followed by active service on 1 March 1943 as part of the 6th Flotilla for the remainder of her service.

In 4 patrols she damaged 1 merchant ship, for a total of and sunk one warship (1,370 tons).

Convoy SC 122
On 19 March 1943, after damaging the Greek freighter Carras, a RAF B-17 Flying Fortress bomber from RAF Sqdn 220 hit the boat with 4 depth charges, causing sufficient damage as to force her to return to France.

Wolfpacks
U-666 took part in 14 wolfpacks, namely
 * Ostmark (6–11 March 1943)
 * Stürmer (11–20 March 1943)
 * Seewolf (21–30 March 1943)
 * Oder (17–19 May 1943)
 * Mosel (19–24 May 1943)
 * Trutz (1–16 June 1943)
 * Trutz 2 (16–29 June 1943)
 * Leuthen (15–24 September 1943)
 * Rossbach (24 September - 6 October 1943)
 * Hela (28 December 1943 - 1 January 1944)
 * Rügen 6 (5–7 January 1944)
 * Rügen (7–26 January 1944)
 * Stürmer (26 January - 3 February 1944)
 * Igel 1 (3–10 February 1944)

Fate
U-666 went missing on 10 February 1944 in the North Atlantic without explanation. All hands were lost.