Legacy of Kain is a series of action-adventure video games primarily developed by Crystal Dynamics and published by Square Enix Europe (formerly Eidos Interactive). The first title, Blood Omen: Legacy of Kain, was created by Silicon Knights in association with Crystal Dynamics, but, after a legal battle, Crystal Dynamics retained the rights to the game's intellectual property, and continued its story with four sequels. To date, five games comprise the series, all initially developed for video game consoles and later ported to Microsoft Windows. Focusing on the eponymous character of Kain, a vampire antihero, each title features action, exploration and puzzle-solving, with some role-playing game elements.

The series takes place in the fictional land of Nosgoth—a dark, Gothic fantasy setting—and revolves around Kain's quest to defy his fate and restore balance to the world. Legacy of Kain: Soul Reaver introduced another antihero protagonist, Raziel; the adventures of both characters culminate in Legacy of Kain: Defiance. Themes of destiny, free will, morality, redemption and the hero's journey recur in the storyline, which was inspired by ancient literature, horror fiction, Shakespeare's plays and Gnosticism. The Legacy of Kain games have enjoyed critical success, particularly receiving praise for high-quality voice acting, narrative, and visuals, and, as a whole, had sold over 3.5 million copies as of 2007. In 2015, a sequel has been confirmed as "50/50".