Celebrity Big Brother 1, also referred to as Celebrity Big Brother 2001, was the first series of the British reality television show Celebrity Big Brother. The show is based on an originally Dutch TV series of the same name created by producer John de Mol in 1997. In honour of Comic Relief, six celebrities entered the Big Brother house.

The series premiered on 9 March 2001, and lasted for a total of eight days. It concluded on 16 March 2001 when comedian Jack Dee was crowned the winner. The series revolved around a group of celebrities living in a custom built house with no contact with the outside world. Each week, the housemates are required to nominate two people for eviction. The two or more people with the most votes were nominated to leave the House. The viewers then decided which of the nominees should leave, with the selected person leaving during a live show. This process continued until only three housemates remained, at which time the public voted for which of them should win the series. Unlike the original show, Celebrity Big Brother saw the housemates competing for charity.