HMS Forfar (F30) was a British ocean liner that was commissioned into the Royal Navy as an armed merchant cruiser in 1939 and sunk by enemy action in 1940. She was launched in Scotland in 1920 as a transatlantic liner for the Canadian Pacific Steamship Company as Montrose. She was one of three sister ships. The others were Montcalm, also launched in 1920, and Montclare, launched in 1921.

German submarine U-99 was a Type VIIB U-boat of Nazi Germany's Kriegsmarine during World War II. She was laid down on 31 March 1939 at the Friedrich Krupp Germaniawerft in Kiel as yard number 593. She was launched on 12 March 1940 under the command of Korvettenkapitän Otto Kretschmer and was assigned to the 7th U-boat Flotilla based in Kiel and later in St Nazaire.