Australia Day is Australia's national day, marking the anniversary of Captain Arthur Phillip's First Fleet raising the British Union Jack at Sydney Cove in 1788. After the Federation of Australia on 1 January 1901, the official recognition and dates of Australia Day and its corresponding holidays emerged gradually and changed many times. Further alternations and alternatives have been proposed for debate, but not yet officially agreed or adopted.

Previously, Australia Day public holidays were held on different dates around Australia (such as a movable Monday or Friday for long weekends) with the first "Australia Day" being designated as Friday 30 July 1915 (as fundraising for World War I), and 26 January having been formerly recognised by different names (prior to 1946) as a regionally-specific date lacking national recognition (prior to 1935) and lacking official celebrations in the nation's own capital.

There have also been proposals to institute a second day specifically for Indigenous Australians in addition to the existing date, which is often referred to as Invasion Day by opponents. Polling has shown a marked shift towards support for a change of date or second day of celebration since 2000, though around two thirds of respondents in recent years have supported the current date. Various proposals for the name and date of a new holiday have been put forward.

Both before the establishment of Australia Day as the national day of Australia, and in the years after its creation, several dates have been proposed for its celebration and, at various times, the possibility of moving Australia Day to an alternative date has been mooted. Some reasons put forward are that the current date, celebrating the foundation of the Colony of New South Wales, lacks national significance; that the day falls during school holidays which limits the engagement of schoolchildren in the event; and that it fails to encompass members of the Indigenous community and some others who perceive the day as commemorating the date of an invasion of their land. Connected to this is the suggestion that moving the date would be seen as a significant symbolic act.

Some Australians regard Australia Day as a symbol of the adverse impacts of British settlement on Australia's Indigenous peoples.

In 1888, prior to the first centennial anniversary of the First Fleet landing on 26 January 1788, New South Wales premier Henry Parkes was asked about inclusion of Aboriginal people in the celebrations. He replied: "And remind them that we have robbed them?"

The celebrations in 1938 were accompanied by an Aboriginal Day of Mourning. The Aboriginal Tent Embassy was established outside Old Parliament House, Canberra, on Australia Day in 1972, and celebrated 50 years of existence in 2022.

A large gathering of Aboriginal people in Sydney in 1988 led an "Invasion Day" commemoration marking the loss of Indigenous culture. Some Indigenous figures and others continue to label Australia Day as "Invasion Day", and protests occur almost every year, sometimes at Australia Day events.