The fourth series of the Australian cooking game show MasterChef Australia premiered on Sunday, 6 May 2012 at 7.30pm on Network Ten. Judges George Calombaris, Gary Mehigan and Matt Preston returned from the previous series. After the first week in Melbourne, the competition took the contestants to places nationally, such as Kangaroo Island and Tasmania, as well as the international destination, Italy. It also featured a number of guest chefs, including Jamie Oliver, Rick Stein and Buddy Valastro.

The fourth series was won by Andy Allen who defeated Julia Taylor and Audra Morrice in the grand finale on 25 July 2012. Andy would later go on to be a judge on the show himself.

For the first time, the initial Top 50 portion of the show took place in and around Melbourne, Victoria. Contestants faced challenges at the Royal Exhibition Building and the South Melbourne Market, and visited Red Hill on the Mornington Peninsula, the Lake House in Daylesford, and Montsalvat in Eltham.

Sunday night challenges returned to the more traditional Mystery Box/Invention Test combination used in the first two series.

After featuring a range of challengers in Series 3 such as contestants and apprentices, Immunity Challenges now typically featured guest chefs (along with a team of helpers) facing off against the chosen contestant plus their choice of two contestant helpers. Both the contestant team and challenging team had to prepare three courses using a core ingredient provided, with the contestants gaining a time advantage (ninety minutes to sixty, for example). Matt Moran acted as a mentor to the contestant team.

There was no Second Chance Cook Off this season, so eliminated contestants had no chance to return.

The Grand Finale featured three finalists instead of two.

After a series of auditions and challenges, the winner was determined on 25 July 2012.