HMS Implacable was a Formidable-class battleship of the British Royal Navy, the second ship of the name. The Formidable-class ships were developments of earlier British battleships, featuring the same battery of four 12-inch (305 mm) guns—albeit more powerful 40-calibre versions—and top speed of 19 knots of the preceding Canopus class, while adopting heavier armour protection. The ship was laid down in July 1898, was launched in March 1899, and was completed in July 1901. Commissioned in September 1901, she was assigned to the Mediterranean Fleet and served with the fleet until 1908. After a refit, she transferred to the Channel Fleet, then onto the Atlantic Fleet in May 1909. By now rendered obsolete by the emergence of the dreadnought class ships, she was assigned to the 5th Battle Squadron and attached to the Home Fleet in 1912.

The Formidable class of battleships were a three-ship class of pre-dreadnoughts designed by Sir William White and built for the Royal Navy in the late 1890s. The class comprised Formidable, Irresistible, and Implacable. They were armed with a battery of four 12-inch (305 mm) guns, they had top speed of 18 knots, and they marked the adoption of Krupp armour in British battleship designs. The class formed the basis for the nearly identical London class of five ships, and those ships are sometimes included in the Formidable class. Formidable, Irresistible, and Implacable were built between 1898 and 1901 at the Portsmouth, Chatham, and Devonport Dockyards, respectively.