Peter Cosgrove is joining a first-time gathering of Commonwealth governors-general in London to celebrate the Queen's 90th birthday.
Sir Peter and Lady Cosgrove will attend a special service of thanksgiving for the Queen at St Paul's Cathedral on Friday before attending a lunch for governors-general at Buckingham Palace.
He told reporters on Thursday he was bringing the congratulations of 24 million Australians to the longest-serving British monarch.
"This is the first time that all of the Commonwealth governors-general have been gathered in London like this to help celebrate and bring the greetings of their nations to her majesty.
"I'm bringing the affection and the respect and the congratulations of all Australians, 24 million Australians, here in London to say to the Queen, `Happy birthday'."
Sir Peter said the Queen had visited Australia 16 times "and those occasions she's become aware that Australians think she's doing a fantastic job and has done for so many years."
Sir Peter and Lady Cosgrove have also been invited to join the Queen and the Duke of Edinburgh to view the Trooping the Colour at Whitehall on Saturday.
