Musashi (武蔵, namesake; former Musashi Province) was, alongside her sister ship Yamato, one of the heaviest and most powerfully armed battleships ever constructed. Armed with massive 46 cm Type 94 main guns—the largest naval artillery ever mounted on a warship—the Yamato-class was built to counter American numerical superiority, free from displacement or width restrictions imposed by the Panama Canal. She was laid down at the Mitsubishi shipyard in Nagasaki on 29 March 1938, launched on 1 November 1940, and commissioned on 31 August 1942. Upon entering service, Musashi served as the flagship of the Combined Fleet alongside Yamato.

Between 1942 and early 1944, Musashi led several sorties into and around various Japanese-occupied islands in search of American forces, though none were successful. After being hit by a torpedo from the submarine USS Tunny (SS-252) on 29 March 1944, Musashi was sent back to Japan for a major anti-aircraft refit, which removed the port and starboard 155 mm secondary turrets in favour of a large number of AA guns. Despite this, when she took part in the Battle of Leyte Gulf on 24 October 1944, Musashi was overwhelmed by the American carrier fleet. She was struck by 19 torpedoes and 17 bombs before sinking, resulting in the deaths of 1,023 crew members. During the battle, Musashi fired her 460 mm guns only once, using anti-aircraft shells, though this action crippled her No. 1 turret due to a jammed gun. The sinking of Musashi signalled the end of the battleship era and heralded the rise of aircraft carriers as the dominant naval flagship.

Musashi was introduced in Update 2.51 "Spearhead" in her 1943 configuration. As with her sister Yamato, Musashi boasts unmatched firepower with her triple 46 cm guns, capable of delivering devastating hits with armour-piercing shells weighing over 1.4 tons each and penetrating more than 600 mm of armour at 15 km. However, as Musashi is presented in her pre-1944 configuration, she lacks the extensive anti-aircraft armament of Yamato and instead retains her full original set of 155 mm secondary guns. While this results in her having a significantly smaller crew, Musashi can arguably absorb more damage than her sister due to the absence of numerous vulnerable AA turrets that would otherwise cost crew each time they were disabled. On the other hand, this lack of AA weaponry leaves Musashi extremely vulnerable to enemy aircraft, and her massive profile makes her an attractive target for bombs and torpedoes alike.