Ernst Mengersen (30 June 1912 – 6 November 1995) was a German naval officer who reached the rank of Korvettenkapitän with the Kriegsmarine during World War II. He was also a recipient of the Knight's Cross of the Iron Cross (German: Ritterkreuz des Eisernen Kreuzes). The Knight's Cross of the Iron Cross was awarded to recognise extreme battlefield bravery or successful military leadership.
World War II
Mengersen commanded the U-18, U-143, U-101 and U-607, and sank twelve ships, including the SS Gairsoppa and HMS Broadwater, on eleven patrols, for a total of 68,071 gross register tons (GRT) of Allied shipping. The Gairsoppa carried 7,000,000 ounces of silver, which was worth £600,000 at the time of its sinking.
Two Knight's Cross of the Iron Cross recipients served as watch officers under Mengersen's command. Egon-Reiner von Schlippenbach served as first watch officer on U-101's fourth patrol under Mengerson, while Karl-Heinz Marbach was Mengerson's second watch officer on U-101.
In June 1943 Mengersen became commander of the 20th U-boat Flotilla based in Pillau, remaining in this position until 24 February 1945. During the last three months of the war, Mengersen served firstly with the 25th U-boat Flotilla and then in April 1945, he was selected to command the new 15th U-boat Flotilla.
- Wehrmacht Long Service Award, 4th class (1 April 1937)
- Spanish Cross in Bronze with Swords (23 October 1940)
- Iron Cross (1939)
- 2nd Class (27 January 1940)
- 1st Class (10 December 1940)
- U-boat War Badge (1939) (25 February 1942)
- Knight's Cross of the Iron Cross on 18 November 1941 as Kapitänleutnant and commander of U-101
- Mentioned in the Wehrmachtbericht on 3 December 1940
- War Merit Cross
- 2nd Class (1 September 1944)
- 1st Class (31 January 1945)
Mengersen survived the war and died in Detmold, at the age of 83.