In Sydney, a citizenship ceremony by the Opera House began with a school choir helping sing a Welcome to Country.
And a multicultural twist to the smoking ceremony that followed.
Cedar leaves from Lebanon, elephant grass from Uganda and jasmine leaves from China were burnt alongside local flora.
The hundred or so new Australians were part of a 17-thousand-strong cohort from more than 145 countries receiving their Australian citizenship.
In Canberra, Prime Minister Malcolm Turnbull began the day by inspecting the Federation Guard and Royal Australian Navy band.
Before telling a group of newly-sworn in Australians the nation is bound together not by history, race or culture but mutual respect.
"We've built a remarkable country. Yes, there have been great leaders in every field who have inspired us, but Australia belongs to all of us. It was built by all of us. Through the love of your adopted country, you too will contribute to our success."
Mr Turnbull says Australians should look at the past with great pride and with some regret - but not be defined, or trapped, by the nation's history.
The head of the Australia Day Council, VC recipient Corporal Ben Roberts-Smith, echoed Mr Turnbull's message.
He called for unity, above all else.
"Australia Day is as much about a nation's past as it is about its future. I encourage you, on this day, Australia Day, to celebrate in an inclusive way and to demonstrate mutual respect and understanding of others. Our nation has been built on its remarkable diversity in all forms. We want an inclusive Australia Day, so let's celebrate our diversity today, our national day, and every day."
In Hobart, Australia Day events were focused on the Annual Sandy Bay Regatta, with a traditional tug of war.
In Darwin, hundreds watched the traditional ute run at the Hidden Valley Raceway.
In Brisbane meanwhile, crowds descended on the Story Bridge Hotel for Australia Day cockroach races.
Speaking after a citizenship ceremony in Melbourne, Opposition Leader Bill Shorten used the occasion to add to calls for an Australian republic.
"It is out of date to remain to remain a constitutional monarchy when we could be a republic and so many political leaders agree. Now is the time, and I call upon Malcolm Turnbull to stand up for what he believes in, for what he said he believes in his whole life. I will work with him."
Sir Peter Cosgrove delivered the annual televised governor-general's address, in which he paid tribute to the common threads which he says bind Australians together.
"Australia is a great country, made so by great people. We should remember today what binds us together: Our values, our identity, our hopes."
