- Class: Schiff 10
- Displacement: 3,862 tons
- Dimensions: 379 x 54 x 23 ft.
- Machinery: 1-shaft geared turbines, S.H.P. 6,500 = 18 knots
- Armament: 6-5.9 in., 2-37 mm. A.A. guns; 4-21 in. T.T.(2x2); 2 aircraft; 90 mines
- Complement: 345
- Builder: Deutsche Werft, Hamburg
- Launched: 1938
- Notes: Originally buit as the freighter Santa Cruz. She was the fourth raider cruiser to leave Germany, on 6 June 1940, under captain Otto Kähler. She claimed six victims in the first 17 days of her cruise. She then encountered the British Armed Merchant Cruiser (AMC) HMS Alcantara on 28 July, and during a 35-minute engagement both ships were damaged, but Thor broke off the action. In the next four months she sank only two more ships, before meeting the British AMC HMS Carnarvon Castle on 5 December 1940. During a tough one-hour engagement, the latter was seriously damaged, and forced to run for Montevideo, while the Thor was not seriously hurt. After four more months at sea and only two additional sinkings, on 4 April 1941 she had her third meeting with a British AMC, HMS Voltaire, and this time pressed her attack until the latter was sunk. Thor then sailed for home, arriving at Hamburg on 6 June, having sunk or captured 12 ships of 96,547 tons in a voyage of 329 days.
Thor had her guns upgraded and radar added, before a second cruise began on 20 November 1941 under the command of Günther Gumprich. She searched unsuccessfully for Antarctic whalers, but then sank five ships in the South Atlantic from March 1942. Shifting to the Indian Ocean, she claimed five more victims, before heading to Japan for replenishment and repairs. She docked at Yokohama on 10 October. On 30 November, she was berthed next to the tanker Uckermark (ex-Altmark when the latter exploded; the subsequent fires burnt out and sank the Thor too. For her second voyage, she was credited with 10 ships of 56,037 tons.