The sails of Sydney's Opera House were lit up with the artwork of Wiradjuri-Biripi artist James P. Simon in one of the many dawn reflections around Australia ahead of January 26 festivities and protests.
Mr Simon's artwork titled River Life depicts the essential and life-giving role of waterways to Aboriginal people.
"Water provides food, medicine, tools, kinship, connection, recreation, stories, songlines and healing.
"Water is seen as a living entity with its own spirit, and it is believed that we have a responsibility to protect and care for it."
People gather for a smoking ceremony at Alfred Square in Melbourne to mark a day of mourning. (Diego Fedele/AAP PHOTOS)
Commemorations are continuing with flag-raising ceremonies before some 20,600 people from 150 countries take the oath of citizenship.
Prime Minister Anthony Albanese on Sunday morning attended a ceremony at Lake Burley Griffin in Canberra, where he received a general salute from the Australian Federation Guard.
Governor-General Sam Mostyn was received with the Vice-Regal Salute and inspected the guard before a citizenship ceremony was held to welcome new Australians.
Mr Albanese praised Australia's democratic values in his speech for the citizenship ceremony.
"We all belong to the same proud story," he said.
"We are all part of a nation built by hope and hard work, aspiration and determination."
Police have vowed to be out in force at demonstrations, with the national day coinciding with the Australian Open men's final in Melbourne.
A child with an Aboriginal flag at an Invasion Day rally in Brisbane. (Jono Searle/AAP PHOTOS)
Invasion Day events, where tens of thousands of people are expected, have kicked off in major capital cities and regional centres.
Victoria Police said they had done "extensive planning" for Australia Day community events and rallies.
"We're well prepared for all major events and will have a highly visible presence throughout the entire CBD to ensure they can occur safely," a spokesperson said.
NSW Police promised to use "proactive policing strategies" to ensure minimal impact on the community.
"The NSW Police Force recognises and supports the rights of individuals and groups to exercise their rights of free speech and peaceful assembly," the force said.
"The first priority for NSW Police is always the safety of the public."
Pro-Palestine activists who usually rally in central Melbourne each Sunday have urged supporters to join the Invasion Day protest march, which will start at state parliament before heading to Flinders Street Station.
Organisers say January 26, the anniversary of the arrival of the First Fleet in 1788, is not a day to celebrate.
Anthony Albanese praised Australia's democratic values in his speech for a citizenship ceremony. (Mick Tsikas/AAP PHOTOS)
In Sydney, protesters are gathering at Belmore Park in Haymarket while in ACT the event will take place at the Aboriginal Tent Embassy.
Activists in Hobart are also marching to state parliament, while other protests and cultural events are also being held in Brisbane, Perth, Adelaide and Darwin.
In Melbourne, a smaller unrelated pro-Australia Day rally is planned outside Melbourne Park which is the home of the Australian Open, however, it's not expected to cross over with other rallies.
Music lovers will descend on Sydney Harbour for the Australia Day Live concert set against the backdrop of the opera house, while other free concerts are being held around the nation.
Heatwave warnings have been issued for Australia Day by the Bureau of Meteorology. (Joel Carrett/AAP PHOTOS)
As many Austrlians attended Australia Day commemorations or protest rallies many others have headed for the beach or barbecues amid rising heat.
Heatwave warnings have been issued across the nation, with alerts current for much of Queensland, northern NSW, parts of South Australia, central Western Australia and southern parts of the Northern Territory.
The Bureau of Meteorology said severe heatwaves can be dangerous for many people including older people, babies, children, pregnant and breastfeeding women and those with medical conditions.
"Seek a place to keep cool, such as your home, a library, community centre or shopping centre," the bureau said.
