Unterseebootsflottille) also known as the Weddigen flotilla, was the first operational U-boat unit in Nazi Germany's Kriegsmarine (navy).

Founded on 27 September 1935 under the command of Fregattenkapitän Karl Dönitz,[1] it was named in honor of Kapitänleutnant Otto Weddigen.

Weddigen, a U-boat commander during World War I, died on 18 March 1915 after his submarine U-29 was rammed by the British battleship HMS Dreadnought in the North Sea.

[2] The flotilla at first only consisted of U-9, a Type IIB boat commissioned on 21 August 1935.

[3] Originally based in Kiel from September 1935 – May 1941, it was moved to Brest, France in June 1941.