Oscar (known by his nickname, Unsinkable Sam, or by the Germanized spelling of his name, Oskar) was a ship's cat who purportedly served during World War II with both the Kriegsmarine and the Royal Navy and survived the sinking of three ships in 1941 - the German battleship Bismarck, and then the British destroyer HMS Cossack and aircraft carrier HMS Ark Royal.

While contemporary reports of the story were widely publicised in 1941 after the sinking of Ark Royal, including photographs of Oscar, there is no firm evidence to link the cat to Bismarck or Cossack.

[3] An interview with three survivors by the Yorkshire Post a few days later quoted a petty officer as saying that "both the ship's cats" had been saved, "Oscar (previously the pet of the Bismarck's crew) and Parry".

)[5] "Oscar" reappeared in the press in early December, when he was reported by the Northern Irish papers to have been taken to the Derry Sailor's Rest and given to the manager there, Margaret Hill of Enniscorthy.

[10] There is no mention of this incident in Ludovic Kennedy's detailed account of the sinking of the Bismarck, suggesting that information later gleaned from sailors regarding the cat's true service was apocryphal.

[citation needed] It has been suggested that the name "Oscar" was given by the crew of the British destroyer HMS Cossack that rescued him from the sea following the sinking of the German battleship Bismarck.

[14]: 170  The initial explosion had blown off one third of the forward section of the ship, killing 159 of the crew; however, Oscar survived this, too, and was subsequently brought to the shore establishment in Gibraltar.

[citation needed] Now nicknamed "Unsinkable Sam", the cat was soon transferred to the aircraft carrier HMS Ark Royal, which coincidentally had been instrumental in the destruction of Bismarck (along with Cossack).