Undead Nightmare

Red Dead Redemption: Undead Nightmare is a 2010 action-adventure game developed by Rockstar San Diego and published by Rockstar Games. A standalone expansion pack to the 2010 open world Western game Red Dead Redemption, it adds a non-canonical, horror–themed single-player campaign, two multiplayer modes, and cosmetic additions to the environments and characters. Set in an alternate timeline from the base game's story, the plot follows returning protagonist John Marston, a former outlaw who sets out to find the cause of and possible cure for a zombie plague that has infected his wife and son. Marston liberates towns overrun by the undead and assists non-playable characters with side quests.

Rockstar Games had a long-standing interest in creating a zombie game. They found the Red Dead Redemption universe and its American countryside to fit the cinematic heritage of the horror film genre. Rockstar wanted their additional content to function outside rather than within the base game's story, but draw on its characters and atmosphere. The company released Undead Nightmare as downloadable content for PlayStation 3 and Xbox 360 platforms on October 26, 2010, and as a retail disc bundle with other downloadable content packs in late November. It was released for Nintendo Switch and PlayStation 4 alongside the main game in August 2023, for Windows in October 2024, and for Android, iOS, Nintendo Switch 2, PlayStation 5, and Xbox Series X/S in December 2025.

Undead Nightmare received generally favorable reviews at its release, and the retail disc sold two million copies by 2011. It was praised as a model for downloadable content and named among the best of the year, with top awards from the 2010 Spike Video Game Awards and Shacknews in this category. Critics praised its production values and handling of the zombie video game motif, and noted its lightheartedness compared to the main game, although some reviewers struggled with the game's character movement controls and found the combat unvaried. It is retrospectively considered to be among the best downloadable content packs ever made.