Hans-Diedrich Freiherr von Tiesenhausen was a German Kapitänleutnant 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.

Von Tiesenhausen was born on 22 February 1913 in Riga, at the time part of the Governorate of Livonia of the Russian Empire, as a member of the Baltic German nobility family Tiesenhausen and son of Gerhard von Tiesenhausen.

He joined the Reichsmarine on 8 April 1934. After undergoing basic military training in the 2nd department (II. Abteilung) of the ship core division (Schiffsstammdivision) of the Baltic Sea in Stralsund, he was transferred to the windjammer training ship Gorch Fock on 15 June 1934, attaining the rank of Seekadett (Naval Cadet) on 26 September 1934.

Promoted Leutnant zur See, von Tiesenhausen served on the light cruiser Nürnberg, taking part in security patrols in Spanish waters in 1937. He then had served with the 5th Marine Artillery Battalion in Pillau.

Tiesenhausen sailed with the U-23 and U-331. He achieved his greatest success as a U-boat commander by sinking the British battleship HMS Barham on 25 November 1941.

On his 3rd patrol U-331 returned to the Egyptian coast.

On 17 November she landed seven men of the Lehrregiment Brandenburg east of Ras Gibeisa, on a mission to blow up a railway line near the coast, which failed.

U-331 was sunk on 17 November 1942, north of Algiers, during "Operation Torch". She had been badly damaged after being attacked by a Lockheed Hudson bomber and signalled surrender, but was attacked and sunk by a Fairey Albacore torpedo-bomber from the British aircraft carrier HMS Formidable. Of her crew 32 were killed and 17 survived including Tiesenhausen. He was a prisoner of war in England and Canada until 1947 when he returned to Germany. He worked as a joiner, but in late 1951 he returned to Canada.

Awards

• Dienstauszeichnung 4th Class (8 April 1938)
• The Return of Memel Commemorative Medal (25 June 1940)
• The Return of Sudetenland Commemorative Medal of 1 October 1938 (6 September 1940)
• Iron Cross (1939)
  • 2nd Class (30 January 1940)
  • 1st Class (7 December 1941)
• Medaglia di bronzo al Valore Militare (November 1941)
• Medaglia d'Argento al Valor Militare (25 March 1942)
• U-boat War Badge (1939) (26 February 1942)
• Knight's Cross of the Iron Cross on 27 January 1942 as Kapitänleutnant and commander of U-331
• Mentioned twice in the Wehrmachtbericht on 26 November 1941 and 27 January 1942