A ninja (忍者) is an enemy type featured in certain Double Dragon games.
Ninjas were first introduced in the NES version of Double Dragon II: The Revenge, where they are middle-class enemy characters. They only appear in two stages: at the end of Mission 2, where the player has to fight a pair of them as part of a boss battle, and later on at the end of the Mission 8, where they're the last group of the enemies that the player face just before the fight against the doppelgangers. They are armed with kunai knives and shuriken stars. They always move by running or jumping and only stand still momentarily. However, there extremely vulnerable to the Cyclone Spin Kick due to their lack of crouching animation.
In Double Dragon III: The Sacred Stones, ninjas appear in Mission 3 as minions of Yagyu Ranzou whom the player must fight throughout the stage. Armed with ninja blades and shuriken stars, their fighting style are similar to Ranzou's, aside from their sliding jump kick. They come in two varieties, light and dark, with the darker ninjas having slighter stronger techniques. They reappear in Mission 5, where the player must fight them in the last room just before the final battle.