Andy Murray and his wife Kim hope to raise cash for cancer sufferers with the sale of a "priceless" tennis ball.
The white ball is one of three in existence that has been signed by both Murray and the late British Wimbledon champion Fred Perry (1909-1995).
Organisers of the online charity raffle say auctioneers have been unable to put a price on the "exceptional" piece of tennis memorabilia.
Funds raised will go to the St Peter & St James Hospice in Wivelsfield, Sussex.
The hospice cared for tennis fan Gail Sargent who met Perry on his visit to Maresfield Tennis Club in 1994 and a decade later gifted a set of three balls he signed to Murray. Ms Sargent, who had ovarian cancer, died in 2010.
In her memory - and after witnessing the cancer battles of his friends Elena Baltacha and Ross Hutchins - Murray decided to add his signature and auction one of the balls to raise cash for the hospice.
Another of the balls has been donated to the Wimbledon Lawn Tennis Museum for display, and the third one Murray and Kim will keep as a piece of tennis history.
The 2013 Wimbledon Champion said: "I am incredibly grateful to Gail for the gift she gave me all those years ago, it didn't seem right to just keep them hidden away. So many people are touched by cancer, so I'm really hoping we can raise a lot of money with this raffle."
The raffle went live today at www.raffleplayer.com/andymurray and will run through to the end of the grass court season.
Tickets are £1 each, with the winning ticket drawn on the day of the Wimbledon final, July 12.
Colin Burgess, chief executive of St Peter & St James Hospice, said: "We are so grateful to Kim and Andy Murray for their generosity and support.
"This unique prize and raffle mean so much to us in this, our 40th anniversary year."
Anna Renton, curator of Wimbledon Lawn Tennis Museum, said: "We are extremely honoured that Kim and Andy have asked us to exhibit such a unique item, and are proud to be supporting this very worthy cause."
Perry won three consecutive Wimbledon Championships from 1934 to 1936. Prior to Murray, he was the last British player to win the men's Wimbledon championship and was the last British player to win a men's singles grand slam title until Murray won the 2012 US Open.