The Princess Royal is one of the "unsung heroes" of any success at the London 2012 Olympics, Games chiefs have said.
London 2012 chairman Lord Coe described Anne's commitment and passion for the cause as "extraordinary" while Olympics minister Hugh Robertson said her impact has been of "inestimable value".
The Princess Royal, who is leading the official British delegation which will collect the Olympic Flame in Athens, ahead of the London Games, is president of the British Olympic Association and has been a member of the International Olympic Committee (IOC) since 1988.
Lord Coe described her as being "absolutely committed to this", adding: "I could not ask more from any board member that I have at Locog (the London 2012 organising committee)."
"Her commitment and passion for this is extraordinary from the very moment that we threw our hat in the ring."
She visited the Therapeutic Riding School of Greece during the trip to Athens with Lord Coe. It helps children and adults with disabilities and is celebrating its 30th anniversary. She watched some of the children do their exercises on the horses.
Anne is the only member of the Royal Family to compete at an Olympics after she took part in the 1976 Montreal Games, riding the Queen's horse Goodwill.
The Princess was part of the three-day eventing team.
She won the 1971 European three-day event championships on Doublet at Burghley, a feat repeated by her daughter Zara Phillips on her horse Toytown at Blenheim in 2005.
Phillips pulled out of the 2008 Olympics when Toytown suffered an injury.