Prime Minister Tony Abbott has conducted his first ever citizenship ceremony, welcoming 24 new citizens to the nation's team as part of Australia Day celebrations.
"Thank you and congratulations, new Australians," Mr Abbott said after leading the group in reciting the oath of allegiance in Canberra on Sunday.
Mr Abbott heard pledges from the 24 who hailed from New Zealand, the UK, Canada, Argentina, the US, Tanzania, Kenya, Sri Lanka, Philippines, France and Denmark.
"To the men and women taking the citizenship pledge here today - and to the almost 18,000 taking the pledge around Australia - I say `welcome to the team'."
Mr Abbott, fresh back from the World Economic Forum in Switzerland, said being Australian was one of the greatest gifts imaginable.
Australia Day marked the anniversary of the arrival of the First Fleet but it was also an occasion to celebrate something richer and deeper, he said.
"We celebrate the nation and the people we have become," he said in his address to the Australia Day flag raising and citizenship ceremony.
Twenty three million Australians had found unity in diversity, respect in differences and have built a modern nation on the idea that anyone can get ahead provided they are prepared to have a go, he said.
"My duty, as your prime minister, is to ensure that, as far as possible, in this great land of ours, no one is left behind," he said.
Governor-General Quentin Bryce said she found it exciting to be part of these ceremonies, with Sunday's formalities her last before her term ends in March.
"There is something very, very special about welcoming new members to our community and uniting all Australians under the values we share," she said.
In Melbourne, Opposition Leader Bill Shorten reflected on how the finest moments in Australian history had come from turning national will towards ending exclusion and bringing people in from the margins.
"Our challenge is to continue the Australian anthem of inclusion," he said.
"From this day on, instead of talking about migration as a threat to the peaceful, multicultural nation we have built, let us see it as the irreplaceable element in the making of modern Australia."