HMS Dunnottar Castle was the 1936 Union-Castle motor liner Dunnottar Castle, requisitioned just before the war and converted into an Armed Merchant Cruiser, pennant F 34.

She was requisitioned by the Admiralty on 30 August 1939, conversion was completed on 22 October 1939, and she was armed with seven 6-inch guns and two 3-inch AA guns. Her listed wartime speed was about 17 knots.

Her early war service was mainly South Atlantic patrol and escort work. Uboat.net gives her career as: South Atlantic Station

Oct 1939–Apr 1940; Freetown Escort Force,

May 1940–Nov 1941; South Atlantic Station again,

Dec 1941–May 1942. She escorted Freetown/Liverpool convoy work, including SL convoys; one detailed example is Convoy SL 72, where she joined on 20 April 1941 and remained with the convoy until 11 May.

On 27 July 1942 she was released from Royal Navy AMC service and passed to the Ministry of War Transport as a troopship. She was converted for trooping duties.

Her troopship work included Operation Torch: in November 1942 she carried troops in Convoy KMF 2 to Algiers, then returned in MKF 2. She continued Clyde–Algiers work into 1943, later going to the eastern Mediterranean after the Italian armistice, reaching Port Said in September 1943 and then carrying troops to Taranto.

She carried over 250,000 men, including cross-Channel shuttle work between Normandy and Southampton after D-Day.