King's Birthday, also known as the Queen’s Birthday, is a public holiday dedicated to the British monarch. However, in the Australian state of Western Australia (WA), it is referred to as the King's Birthday, a testament to its historical links. As the name suggests, this holiday is celebrated in honor of the current British monarch's birthday.

In most parts of Australia, the holiday is observed on the second Monday of June. However, in Western Australia, the King's Birthday is usually celebrated either at the end of September or the beginning of October. Akin to other states, the exact timing of the King's Birthday in WA is not correlated to the actual birthday of the reigning monarch but is rather a fixed day designated for celebration.

On the King's Birthday in WA, various celebrations are held in lieu of the reigning monarch's birthday. These customarily include community and sporting events, outdoor festivals, concerts, and firework displays. The day also serves as a means to honor historical links between the United Kingdom and Australia, and provide Australians with the opportunity to demonstrate their respect and admiration for the monarchy.