The Queen's oldest granddaughter, Zara Phillips, has got engaged to her long-term boyfriend, England rugby union player Mike Tindall.
Buckingham Palace said Mr Tindall, 32, had proposed on Monday at the couple's Gloucestershire home.
Miss Phillips, 29, who is 12th in line to the throne, said she was "shocked", but "very happy"; the Queen and Duke of Edinburgh said they were "delighted" by news of the engagement.
No wedding date has yet been set.
The announcement comes just weeks after Prince William and Kate Middleton revealed that they were engaged and planned to marry on 29 April 2011.
BBC correspondent Nicholas Witchell said as public attention focused on the prince's wedding, that of his cousin and Mr Tindall was likely to be a largely private event.
He added: "Zara is not a working member of the Royal Family and has been able to live her life with a considerable amount of freedom.
"There has been a rebellious streak, with her infamous tongue stud, but Mike Tindall has been a steadying influence on Zara."
Miss Phillips and Mr Tindall met during England's Rugby World Cup-winning campaign in Australia in 2003.
He also plays for Premiership side Gloucester and was named club captain for the 2010/11 season in August.
In a statement, he said: "I am delighted that Zara has agreed to marry me. We are both very excited about the next stage of our lives together."
His bride-to-be added: "I was really shocked when Mike proposed but I am very happy."
Miss Phillips has achieved sporting success in her own right, winning individual gold in three-day eventing at the World Equestrian Games in Germany in 2006.
The title helped her become BBC Sports Personality of the Year later that year, following in the footsteps of her mother, Princess Anne, who won the award in 1971.
Clarence House issued a statement on behalf of the Prince of Wales, the Duchess of Cornwall, Prince William and Prince Harry.
It said: "Their royal highnesses are delighted with the news and look forward to conveying their best wishes to the couple."