Ninja Gaiden, released in Japan as Ninja Ryūkenden (Japanese: 忍者龍剣伝, literally "Legend of the Ninja Dragon Sword") and as Shadow Warriors in Europe, is a side-scrolling cinematic action-platforming video game. Tecmo developed and published it for the Nintendo Entertainment System (NES); its development and release coincided with the beat 'em up arcade version of the same name. It was released in March 1989 in North America.

The story follows a ninja named Ryu Hayabusa as he journeys to America to avenge his murdered father. There, he learns that a person named "the Jaquio" plans to take control of the world by unleashing an ancient demon through the power contained in two statues. Featuring platforming gameplay similar to Castlevania, players control Ryu through six "Acts" that comprise 20 levels; they encounter enemies that must be dispatched with Ryu's katana and other secondary weapons.