Prime Minister Kevin Rudd says all Australians will share the royal family's joy on the arrival of a baby boy for the Duke and Duchess of Cambridge.
The young royals' first child was born overnight Australian time.
Mr Rudd says it's a happy day for the nation's close friends in Britain and across the Commonwealth.
"On behalf of all Australians, Therese and I extend our warmest regards to the new parents, Prince William, Duke of Cambridge, and Catherine, Duchess of Cambridge," he said in a statement.
"We share in the joy of the Royal Family, particularly Prince Charles on the birth of his grandson and Queen Elizabeth II on the birth of her great-grandchild."
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Mr Rudd said Prince William held a special place in the hearts of many Australians given his first visit down under as a baby himself.
"In more recent times, Prince William demonstrated deep compassion when he met with families in Victoria who had lost everything during the Black Saturday bushfires of February 2009," Mr Rudd said.
