Ninja Gaiden, later released in Japan as Ninja Ryūkenden (忍者龍剣伝, lit. "Ninja Dragon Sword Legend") and in Europe as Shadow Warriors, is a 1988 side-scrolling beat-'em-up originally released by Tecmo as a coin-operated arcade video game. It was first released in North America, and Europe in 1988 and in Japan in 1989. The Ninja Gaiden arcade game was produced and released almost simultaneously with its home console counterpart for the Nintendo Entertainment System, although they are different games with only a few similarities. The designer of the game is only credited as "Strong Shima", but Masato Kato, who worked on the NES Ninja Gaiden, identified him as one Mr. Iijima.
Home versions of the Ninja Gaiden arcade game were released in Europe under the Shadow Warriors title in 1990 by Ocean Software for five different computer platforms (Amiga, Atari ST, Commodore 64, ZX Spectrum, and Amstrad CPC) and in North America for IBM PC by Hi-Tech Expressions. An Atari Lynx version was also released. The arcade version of Ninja Gaiden is also included as a hidden bonus game in Ninja Gaiden Black for the Xboxin 2005. The arcade game was published as a Virtual Console game for the Wii in 2009.