Castaways are the contestants who participate in each season of Survivor. Each season ranges from having 16 to 20 castaways, each competing to become the Sole Survivor of the season. Each castaway would be assigned on a tribe (either by the production's choice or by Schoolyard Pick by the contestants themselves), although there are times that tribes aren't assigned on the first day, and there is an instance in Survivor: Palauwhere two castaways, Jonathan Libby & Wanda Shirk, were eliminated before tribes were assigned.
The castaways have to compete in a secluded region (e.g. an island, savannah) where they have to stay there for 39 days (except in Survivor: The Australian Outback, where it was 42 days), avoiding elimination. The castaways compete in two kinds of challenges: Reward Challenge, where the tribe, a single or a group of castaways could win for a reward like tools for the camp, food, or a trip on spots outside the game; and Immunity Challenge where castaways vie for Tribal Immunity where their current tribe would be exempted from Tribal Council, or Individual Immunity where individual(s) can't be voted out in Tribal Council. At the last day of competiton, the Final Two or the Final Three castaways would face the recent castaways eliminated in the game in Final Tribal Council which consists the Jury, who would have the power to choose which of the remaining castaways would become the Sole Survivor.
Castaways usually carry in the game clothes and a bag, where they are sometimes allowed to carry a luxury item. The castaways are also instructed to wear their Buffs all the time to make viewers distinguish easily what tribe each castaway is assigned to. The Jury members that are sent to the sequester site known as Ponderosa could wear new clothes and use the items they have brought that are not allowed to keep while during in the game.
There are currently 406 castaways who have played Survivor (200 male castaways, 206 female castaways).
Of all the castaways, 59 have participated in multiple seasons, with 43 castaways of the 59 castaways competing twice, 14 castaways competing three times and 2 castaways competing four times (Rob Mariano, Rupert Boneham). They are known as Returning Players.
Of all the castaways, 21 of them have been eliminated due to medical concerns or voluntarily ejecting themselves from the game. Two players (Jenna Morasca and Susan Hawk) quit on their second attempt at the game, while two other players (Jonathan Penner and James Clement) were medically evacuated on their second attempt. Dana Lambert is unique for being the first castaway to be eliminated due to having medical concerns, but quitting due to still being allowed to continue while checking with the condition.
If certain information from the outside world is urgently needed to be relayed a castaway (e.g. death of a family member), the contestant must be pulled out from the game before knowing the said information.
Host Jeff Probst said the reason for the number of castaways increasing over the years is to provide "wiggle room", if a cast member is medically evacuated or quits.