Big Brother Australia 2012, also known as Big Brother 9, was the ninth season of the Australian reality television series Big Brother. It was the first to air on the Nine Network who signed a deal with Southern Star Group in September 2011 to broadcast the show.^[1] The season began with a pre-recorded launch show on 13 August 2012.^[2][3][4] Benjamin Norris was announced the winner of the ninth season on 7 November 2012, making him the first openly gay person to win Big Brother Australia. Benjamin proposed to his boyfriend, also named Ben, during the show's finale.^[5]

This season introduced Sonia Kruger as the new host of Big Brother. Mike Goldman continued his role of providing voice over narration for the show.^[6] The production was based at the same compound, located within the Dreamworld theme park, that had been used in all previous series of Big Brother Australia. This season also use some of the game mechanics from the Secret Story franchise.

After four years off air, the Nine Network confirmed on 9 September 2011 that they had signed a contract with Southern Star Group to air the series in 2012; the first time a broadcaster other than Network Ten has broadcast the show in Australia.^[1] In September 2011, when the location of the Big Brother compound had not yet been officially confirmed, Queensland Premier Anna Bligh stated that she would do everything possible to see the show return to the Gold Coast.^[7] A spokesperson from Dreamworld, the original home of Big Brother, stated on 21 September 2011 that nothing was locked in but that the theme park would welcome the return of the show.^[8] In December 2011, The Daily Telegraph reported that Fox Studios Australia and Warner Bros. Movie World had also expressed interest.^[9][10] In an interview ahead of the season launch, Kruger suggested that Big Brother would be family friendly and air at 7.00 pm.^[11]

Several days after the news Big Brother was to return, Southern Star Group announced on their casting website that they would be accepting pre-audition applications for people who were interested in participating on the season.^[12] The official Facebook page for the show, as directed to by the Southern Star website, was opened on 15 September 2011.^[13] On 22 February 2012, it was officially announced that Big Brother would return to Dreamworld in 2012.^[14] Auditions began on 15 March, and took place in all major capital cities, as well as Gold Coast, in April and May 2012.^[15] More than twenty thousand people applied to be on the ninth season.^[16] The Official Big Brother Australia website reported that 14 housemates would be entering the house after going into lockdown on 4 August.^[17]

Big Brother Australia is based on the international Big Brother series produced by Endemol in the Netherlands which began in 1999. The show's name comes from George Orwell's novel Nineteen Eighty-Four (1949), which revolves around a dystopia in which dictator Big Brother is the all-seeing leader. The series generally constitutes 14 or more contestants who live in an isolated house for several months. Housemates are at all times under the control of Big Brother, a rule enforcing authority figure who monitors behaviour of the housemates, sets tasks and punishments and provides the mechanism for contestants to make external requests. Each week, the housemates will cast votes to nominate two other housemates for eviction using five nomination points inside the Nominations Room. These points can be allocated however a housemate wishes (either 4 points to one housemate and 1 point to another; or 3 points to one and 2 points to another). Housemates are not permitted to discuss nominations. The three (or more in the case of a tie) housemates with the most nomination votes will be nominated. The viewers will then decide which of the nominees is evicted. This process continues until only one housemate remains to win the grand prize of $250,000.

This season each of the original fourteen housemates entered with a secret. The task in the first week was for the female housemates to match up the male housemates with their secrets.^[1][3][18] The secrets were that: one has the IQ of a genius (Michael), one became scared of birds after an emu attack (Bradley), one has been fired from every job he's ever had (Benjamin), one hasn't had a girlfriend since he was 11 (Ryan), one was a juvenile offender (Ray), one has dated more than 100 women (Josh), and one is a multimillionaire (George).^[19] The following week the girl's secrets were revealed for the male members of the house to solve. The secrets were that: one had Obsessive Compulsive Disorder (Charne), one was a champion weightlifter (Angie), one is a high school dropout (Estelle), one was a nude protester (Sarah), one used to be an emo (Zoe), one was a hand model (Stacey) and that one is a member of a royal family (Layla).^[20]

The purpose-built house was located at Dreamworld on the Gold Coast, Australia.

Rooms/Areas in the house included:

• Diary Room
• Nominations Room
• HMAS BB/ "Captain's Quarters" (the Rewards Room) – Housemates were granted access to "The Captain's Quarters" along with a sauna and a pool as a reward for winning the "Captain's Challenge". They were able to invite along one housemate of their choice.
• Backyard
• Living room
• Kitchen/dining area
• The utility room, a regularly renovated room that has been used as six separate rooms:
  • The parlour
  • The man-cave
  • A cafe
  • A Switzerland-style room.
  • Also, the hallway to the utility room was used as part of "The Factory" task.
  • A zen temple
• Bedroom, along with storage shelves to store the housemates' possessions
• Bathroom
• Secret executive bathroom, accessed via a secret door in the bedroom disguised as a shelf
• Gym and fitness area
• "The Naughty Corner" – A small room that housemates were sent to if they had broken the house rules (such as excessive swearing or talking without a microphone). Fellow housemates were able to see into the room via a window that could change from being opaque to transparent. On Day 71, Estelle was called the nicest housemate, and thus got to go into the revamped corner, now called 'The Nice Corner.'
• Outdoor entertainment complex/outdoor pizza oven

The house contained rolling cameras hidden behind one-way mirrors which had been situated around the house walls. This was done so that camera operators did not roll cameras around the house.

On launch night, ten housemates (seven women and three men) entered the house on Day 0. The seven women first entered through a room called the parlour for a secret task, but later entered the house. Two more male housemates entered the house on Day 2, two via a live special, and two more revealed on the next day's show. After Week 5's and Week 6's nominations, a female and male intruder entered the house. Ava entered on Day 29, and Sam entered on Day 36. Unlike the original fourteen housemates, no intruders are keeping a secret in the house.

On Day 59, Josh was called to the Captains Quarters, where he was taken out of the house to see his parents. They told him of the sudden death of his only sibling, Toby. Josh spent the night outside of the house, where he made the decision to stay with his family and not return to the house. On Day 60, housemates were informed of the situation, and said their goodbyes in the early hours of Day 60. Out of respect for Josh and his family, Big Brother turned the cameras off for these goodbyes. As a result of Josh leaving, voting lines for eviction were closed—with any votes cast prior being invalidated—and the funds donated to the Salvation Army; a choice by Josh and his family. Also, the weekly challenge was ended prematurely and live feeds from the official website were paused. The upcoming eviction was also canceled, instead replaced with Josh's return to say thank you to the public for their support which was followed by the routinely used 'highlights' show.

This series, housemates were allowed to distribute five nomination points between their two nominations, with a maximum of four points to be allocated to one housemate. The three or more housemates with the most votes face the public vote to save. In addition, nominations are now held in a sound-proof chamber inside a Nominations Room, as opposed to the Diary Room.

Throughout the series, some of the shows aired as specials; apart from the launch, daily shows, nomination shows, eviction shows, and the final.

The launch ratings for this season were up significantly from 2008 as the opening night show reached 2.1 million viewers at its peak and averaged at 1.6 million viewers, the franchise's highest ratings since the 2003 series.^[22]

Ratings are rounded to the nearest ten thousand. Shows on GO! are not included in official averages. Figures in bold include consolidated viewing figures.