Ninja Spirit, known in Japan as Saigo no Nindō[a], is a 1988 side-scrolling hack and slash game developed and released in arcades by Irem.

Although praised by gamers for detailed graphics, serious themes, solid controls and gameplay, the game also was criticized for its harsh difficulty.

The ninja is always armed with the katana named Muramasa (meaning Righteous Cloud), which can be fluidly used to attack in all directions.

The game's hero, Tsukikage (月影), is a young ninja who lost his father to a mysterious half-man half-beast creature.

[8] In Japan, Game Machine listed Ninja Spirit on their September 1, 1988 issue as being the fifth most-successful table arcade unit of the month, outperforming titles like The Main Event.