Metroid is an action-adventure game developed by Nintendo R&D1 with Intelligent Systems and published by Nintendo, released in Japan on August 6, 1986, first for the Famicom Disk System and later the Nintendo Entertainment System. It follows Samus Aran, a bounty hunter in a powered suit, as she explores the caverns of the planet Zebes alone, hunting the parasitic Metroids and the Space Pirates who would weaponize them.

Zebes is one continuous, hostile map of shafts and corridors that open only as Samus finds new abilities, a structure later named the Metroidvania after this game and Castlevania. Its moody isolation and the ending that reveals the hunter beneath the armor made it a landmark of the medium; the series it began still bears its name.