|Developer(s):||Rockstar San Diego|
|Date takes place:||1911|
|Location:||America and Mexico|
- "Unleashed upon the world of Red Dead Redemption. The Undead Nightmare Pack features an entirely new single-player campaign that follows John Marston as he tries to find a cure for the highly-infectious undead plague spreading across the frontier. In addition to this epic single-player adventure, the Undead Nightmare Pack also features a brand new multiplayer mode in addition to new gameplay mechanics, weapons, undead animals and mythical creatures."
Undead Nightmare features the game world from the base game Red Dead Redemption, with the addition of numerous zombie-related elements, including random zombie encounters, missing persons missions instead of bounties and graveyards to purify.
Players can hunt zombie animals such as cougars, bears and wolves and mythical creatures such as Sasquatch, Chupacabra and a unicorn. The Four Horses of The Apocalypse can also be found and used as mounts, each having their own unique ability. The game also introduces new weapons for the player to use. You can now loot zombies/zombie animals for parts, which can be used to create ammunition for the blunderbuss. 
Undead Nightmare introduces new multiplayer features, including "Undead Overrun", in which up to four players must work together to fend off increasingly difficult waves of zombies against the clock. It also introduces "Land Grab", a new feature for free roam, in which players must hold a territory in one of seven major towns for a set amount of time, defending their territory from attackers. The player at the end who held it for the most time as well as having the most kills gets the majority of the awarded points. It also includes 8 new zombie skins for multiplayer and titles that can be unlocked via undead overrun challenges.