The King's Birthday is a public holiday in Australia that is celebrated in all states and territories, with the exception of Queensland and Western Australia. This holiday is meant to honor the reigning British monarch, which has been a tradition in Australia since the late 18th century. Currently, the holiday is associated with the birthday of Queen Elizabeth II, even though her actual birthday is on April 21; the holiday is observed on the second Monday in June.

The King's Birthday is an opportunity for Australians to show their respect for the monarchy. Various events are held throughout the country to celebrate. These might include community events, outdoor activities, and private parties. In the states of ACT, New South Wales, Northern Territory, South Australia, Tasmania, and Victoria, most people take advantage of the holiday to rest and relax, as it is one of the few public holidays that is uniformly observed in these areas.

Notably, in Queensland and Western Australia, this holiday is not observed. Instead, they celebrate the Queen’s Birthday on a different date. The specific date varies from year to year, as it is linked to the date of Labor Day, which can change depending on the state. This makes the King's Birthday a unique holiday in Australia, as it centers around a figure of royal importance, but its observance varies significantly from region to region.