HMS Formidable, the third of four ships of that name to serve in the Royal Navy, was the lead ship of her class of pre-dreadnought battleships. Commissioned in 1904, she served initially with the Mediterranean Fleet, transferring to the Channel Fleet in 1908. In 1912, she was assigned to the 5th Battle Squadron, which was stationed at Nore.
Following the outbreak of World War I, the squadron conducted operations in the English Channel, and was based at Sheerness to guard against a possible German invasion. Despite reports of submarine activity, early in the morning of 1 January 1915, whilst on exercise in the English Channel, Formidable sank after being hit by two torpedoes. She was the second British battleship to be sunk by enemy action during the First World War