The Four-Tribe Format is a tribe division twist that increases the number of competing tribes during the pre-merge phase of the game from two to four. It is an alternative twist to the more frequent Three-Tribe Format, and has so far featured in Survivor: Seychelles and Survivor: Solomon Islands.
Following the introduction of the three-tribe format in Survivor: All-Stars, the four-tribe format was introduced to see if that would have an even bigger impact on the dynamics and create interesting alliances and votes. Survivor: Seychelles therefore became the first season to adopt four tribes with a large newbie cast, the first 20-person cast in the Second Generation. The twist was not seen again for twenty-four seasons until it's reappearance in Survivor: Solomon Islands, this time with an expanded 24-person cast comprised of returning players.