Alcyon was a French fishing trawler that was seized in World War II by the Kriegsmarine for use as a harbour defence boat and later a vorpostenboot, serving as Boot 10 Alcyon and V 420 Alcyon. She was bombed and sunk in the Gironde on 3 August 1943.
Alcyon was 132feet long, her beam was 21.6feet, and her depth was 12.6feet.[1] Her draught was 3.56m (11.68feet). Her tonnages were and . She had a single screw propeller. She had a three-cylinder triple expansion steam engine, made by Alblasserdamsche Machienfabriek, Alblasserdam, South Holland, Netherlands. It had cylinders of 13inches, NaNinches and 35inches diameter by 24inches stroke; was rated at 60 nhp;[1] and gave her a speed of 10kn.
Bonn & Mees of Rotterdam, South Holland built Alcyon as yard number 163 by in 1904 for French owners. Her code letters were OBNH,[1] and her port letter and number were B 2892. By 1930, she was owned by Bourgain-Vincent, Boulogne-sur-Mer.[1] In 1934, the call sign FNOH superseded her code letters. She was sold to E. Malfoy & Fils in that year.[2]
On 26 June 1940, Alcyon was seized by the Germans at La Rochelle, Charente-Inférieure. She was allocated to the Hafenschutz-Flotille Lorient on 2 November, serving as Boot 10 Alcyon. On 4 May 1942, Alcyon was redesignated as a vorpostenboot. She was allocated to 4 Vorpostenflotille as V 420 Alcyon. On 2 August 1943, she was sunk in the Gironde in an attack by British aircraft with the loss of five of her crew.[3]