Fallout: New Vegas Factions

Major Factions
The following factions are the 3 major players in New Vegas. During the course of the game, you will eventually have the option to side with one of them, or go it alone, to the expense of your relations with the other major factions.
 * New California Republic
 * Caesar's Legion
 * Robert House

Minor Factions
The following factions can be recruited as allies (of you and the major faction you ally with, if any) in the climactic battle.
 * Boomers
 * Brotherhood of Steel
 * Followers of the Apocalypse
 * Great Khans
 * Enclave Remnants

The Strip Factions
In addition to the Brotherhood of Steel and the Great Khans, the following are parties you can choose to destroy or spare if you choose to go it alone instead of siding with one of the 3 major factions. All three of these factions run casinos on The Strip.
 * Chairmen
 * Omerta
 * White Glove Society

Other Factions

 * Merchants
 * Crimson Caravan
 * Van Graffs
 * Gun Runners
 * Raider Gangs
 * Fiends
 * Jackals
 * Vipers
 * Towns
 * Goodsprings
 * Freeside
 * The Strip
 * Novac
 * Others
 * Bright Brotherhood
 * State of Utobitha
 * Kings
 * Powder Gangers
 * Ghost People