Fallout New Vegas was announced moments ago during a Bethesda press conference in London.
The new game was revealed by Bethesda's Pete Hines who said that the publisher is working with Obsidian Entertainment on the title.
It will be coming out next year for the PC, Playstation 3 and Xbox 360.
"It is not a sequel to Fallout 3," Hines said. "It's simply another Fallout game in that universe."
It will be the same sort of role-playing game experience seen in Fallout 3, he said. The game's official reveal, with more details and a look at the game down the line.
Hines added that this title will have no impact on what Todd Howard and his team are working on.
Obsidian Entertainment is the development studio that rose from the ashes of Black Isle Studios, responsible for developing Star Wars: Knights of the Old Republic II: The Sith Lords, Neverwinter Nights 2, Alpha Protocol, and Sega's Aliens: Crucible RPG, which is currently on indefinite hold.