Blohm & Voss Ha 139 V2 "Nordmeer" four-engined floatplane shipborne catapult launch in 1937

The Blohm & Voss Ha 139 was a four-engined, all-metal, inverted gull wing floatplane, designed and built by the German aircraft manufacturer Blohm & Voss. At the time of the first aircraft's completion, it was one of the largest float-equipped seaplanes to have been built.

Development of the Ha 139 started in 1935 to fulfil a specification issued by the German flag carrier Deutsche Luft Hansa. Built to serve on the airline's long distance routes, it was equipped with four hydraulically-actuated landing flaps, was powered by four Junkers Jumo 205C diesel engines, and was suitable for catapult-assisted takeoffs. The Ha 139A was promptly followed by the Ha 139B, a variant that possessed greater size and weight. Development of the aircraft led to a land-based version, the Blohm & Voss BV 142 and a proposed reconnaissance/bomber variant of the Ha 139 for the Luftwaffe was never realized.

During October 1936, Ha 139 V1, the first aircraft, performed its maiden flight. Between 1937 and 1939, the type was flown by Deutsche Luft Hansa on various transatlantic routes, predominantly in the South Atlantic. Such flights ceased following the start of the Second World War; the aircraft were adopted by the Luftwaffe and used for military purposes during the conflict. Its service life was cut short by a lack of components; no aircraft survived the conflict.