The Anzac spirit continues to inspire Australian servicemen and women in current conflicts across the world, the Sydney dawn service has been told.
Tim Barrett, Commander Australian Fleet, gave the Anzac Day address to a sombre crowd at Martin Place.
"It was on this day that Australia's national identity was forged in the courage and determination of our young men," he said.
"Their fighting prowess, irrepressible humour and sense of mateship would come to symbolise the triumph and the spirit over adversity and defeat.
"It is this Anzac spirit that shows us not who we are intrinsically as Australians but who we want to be as a nation.
"It has inspired Australian servicemen and women for almost a century and it continues to inspire those who are right now deployed to conflicts across the world serving our nation.
"It is a time to think of the 3000 or so men and women of the Australian Defence Force who are currently serving with great distinction overseas from South Sudan, Egypt to the Middle East, Afghanistan, in the Southeast Asian region and the South Pacific."
Thousands of people packed the entire length of Sydney's Martin Place for the 98th anniversary of Australia and New Zealand forces making their first landing at Gallipoli in Turkey.
Among those in the crowd was Blue Mountains resident Michael Adams, who was draped in military medals.
"My father was in World War II in New Guinea and my great grandfather was killed over in France in 1917 so I come here every year to honour them, as well remember those who have been left behind," Mr Adams said.
Wreaths were laid at the Martin Place cenotaph by Sydney Lord Mayor Clover Moore, NSW Premier Barry O'Farrell, state Opposition Leader John Robertson and federal MP Tanya Plibersek.