Anzac Day commemorations are held each year in the neighbouring countries on April 25 to mark the anniversary of the ill-fated landing of the Australian and New Zealand Army Corps (ANZAC) at Gallipoli in World War I.
Deputy Prime Minister Wayne Swan said almost a century after the start of the Great War, the Anzac tradition was stronger than ever.
"One need only look at the commemorations around the country to see the many young faces in the crowds," he said in remarks to a dawn service in Brisbane, one of many held around the country.
"It's the one day of the year where we as Australians truly unite, where we come together as a nation of equals, no matter who we are, how old we are or where we've come from."
Veterans and their families thronged Sydney's Martin Place for the dawn service, followed by a parade through the city streets in which about 20,000 serving and former military personnel were expected to take part.
Although no allied WWI soldiers survive, with the last combat veteran Claude Choules dying last year aged 110, spectators burst into spontaneous applause for the oldest war veterans as they were driven along George Street.
In Gallipoli, now part of modern-day Turkey, Prime Minister Julia Gillard spoke at a moving dawn service which was broadcast live on Australian television.
More than 10,000 New Zealand and Australian servicemen died in the failed eight-month campaign on the peninsula, and Gallipoli has become a defining symbol of courage and comradeship for the two nations.
"We remember what the Anzacs did in war," Gillard said.
"And for what they did to shape our nation in peace. In this place, they taught us to regard Australia and nowhere else as home."
In New Zealand, about 3,000 people attended a service in Wellington at which the French ambassador to the country, Francis Etienne, spoke of the importance of remembering Gallipoli, noting that France also lost more than 10,000 soldiers there.
"Enemies of a century ago have become the friends of today. This is the reason why it is so important to remember," he said. "The worst of conflicts can lead to the most... enduring peace."