Big Brother is an American television reality competition show based on the original Dutch reality show of the same name created by producer John de Mol Jr. in 1997. The series takes its name from the character in George Orwell's 1949 novel Nineteen Eighty-Four. The American series launched on July 5, 2000, on CBS and, with the discontinuation of the Spanish version in 2022, is currently the longest-running adaptation in the Big Brother franchise airing to date.

The show broadly follows the premise of other versions of the format, in which a group of contestants, known as "HouseGuests", live together in a specially constructed house that is isolated from the outside world for a cash prize of $500,000 (or $750,000 in the 23rd season onwards). The HouseGuests are continuously monitored during their stay in the house by live television cameras as well as personal audio microphones. Throughout the course of the competition, HouseGuests are evicted from the house, by being voted out of the competition. In its inaugural season (which followed the original Dutch format and audience voting determined evictees and the eventual winner), ratings declined and critical reaction grew increasingly negative, prompting the series to be revamped for the second season, which focused on competition and gameplay.A twenty-fourth season of the series premiered on July 6, 2022. On September 25, 2022, CBS renewed the series for a twenty-fifth season, which premiered on August 2, 2023.The show also produced three spin-offs: Big Brother: Over the Top, which aired for one season and was the first reality game show to air exclusively on a streaming platform airing in Fall 2016 on CBS' streaming service, CBS All Access (now Paramount+); Celebrity Big Brother, which first aired on CBS in February 2018.; and Big Brother Reindeer Games, which aired for one season on CBS in December 2023.