Big Brother (Australian TV series) season 4

The fourth season of the Australian reality television series, Big Brother, also known as Big Brother 2004, was aired on Network Ten, starting on Sunday 2 May 2004, with the housemates entering the day before, and ended on Monday 26 July 2004, lasting 86 days. The season was billed as "back to basics, but with one small secret". In a return to the basic format of the first two seasons, which had been eschewed in favour of twists and surprises in the previous season, all housemates were let into the house together and former surprise elements such as swimming pools and gym equipment were all exposed from the beginning.

The only main twist of the series was the prize money - which was raised from $250,000 to $1,000,000, but this was kept hidden from housemates until later in the season. Evicted housemates also received larger prizes than any season before, with every evictee receiving a top of the range Mitsubishi Lancer VR-X. The fourth season saw a change in the voice of Big Brother. Peter Abbott, who had provided the voice for the series from 2001 to 2003, departed the role prior to the 2004 season. The voice was subsequently provided by Nick Colquhoun, who had a more stern tone than in earlier years. However, the stricter and more authoritarian portrayal of Big Brother that became prominent in later seasons had not yet fully developed, with the harsher disciplinary style and frequent fines becoming more associated with the 2005–2007 series.

Two Intruders entered the house later in the game, and Miriam Rivera, the transgender star of the show There's Something About Miriam, entered as a houseguest near the end. The two Intruders were some of the least liked in all the four seasons, with Violeta being chosen for eviction by every single housemate, and then Monica, who already had a boyfriend outside, immediately started falling for Ryan, and she and Bree developed rivalry towards each other. When Monica was finally up for eviction, she was evicted with a large percentage of the votes. Mid-season, the housemates were able to see the unofficial premiere of The Day After Tomorrow. The final contestants in 2004 were Bree Amer and Trevor Butler. Trevor won, and then proposed to his girlfriend on stage. The winner announced of the finale was watched by 2.864 million Australian viewers.