Eternal Darkness: Sanity's Requiem is a psychological horror action-adventure video game developed by Silicon Knights and published by Nintendo. Originally planned for the Nintendo 64, it was switched to the GameCube for development and released on June 24, 2002. It is the first M-rated game published by Nintendo as well as their first game released after Satoru Iwata became President of Nintendo. While the game features similar gameplay mechanics to that of Resident Evil, it distinguishes itself with unique features, such as "sanity effects". In the game, players take on the role of several characters as they battle a powerful entity who seeks to enslave humanity.

Eternal Darkness was widely praised by reviewers and won numerous awards but was not a commercial success. A direct follow-up to the game was cancelled by Nintendo, who was the publisher and owned the game's copyright and trademark, and Silicon Knights a decade later went bankrupt and disbanded. Attempts by the game's writer and director Denis Dyack to make a spiritual successor entitled Shadow of the Eternals failed both of their Kickstarter campaigns, leading to the project being placed on indefinite hold.