Ninja Gaiden Shadow, released in Japan as Ninja Ryūkenden GB: Matenrō Kessen (Japanese: 忍者龍剣伝GB 摩天楼決戦, literally "Legend of the Ninja Dragon Sword GB: Skyscraper Showdown") and in Europe and Australia as Shadow Warriors, is a side-scrolling action game released for the Game Boy in 1991 by Tecmo. It is a prequel to the NES Ninja Gaiden trilogy.

Ninja Gaiden Shadow features simplified play mechanics compared to those used in the NES trilogy. In contrast to the variety of ninja arts and power-ups available in the NES games, Ryu only has a basic sword attack and a Fire Wheel attack that can be replenished for up to five uses. While Ryu cannot stick to or climb walls like in the NES games, he can hang onto railings and move underneath them like in Ninja Gaiden III: The Ancient Ship of Doom, and use both his sword attack and the Fire Wheel art while hanging onto railings. Unique to this installment, Ryu is equipped with a grappling hook that allows him to latch onto hard-to-reach railings. Like in the NES versions, Ryu can find health potions, fire wheel stocks, and extra lives by destroying item containers.