Princess Anne's son Peter Phillips is to marry his girlfriend, Autumn Kelly, Buckingham Palace has announced.
The couple have kept a low profile since meeting in 2003
Peter, 29, is the only son of Princess Anne and her first husband, Captain Mark Phillips.
Rugby player Peter lives with his Canadian girlfriend Autumn, 31, in a cottage on his mother's Gloucestershire estate, Gatcombe Park.
The low-profile couple first met each other at the Canadian Grand Prix in Montreal in 2003.
A Buckingham Palace spokesman said: "The Princess Royal and Captain Mark Phillips are pleased to announce the engagement of their son Peter Phillips to Autumn, daughter of Mr Brian and Mrs Kitty Kelly."
Autumn, a management consultant, moved to Britain after meeting Peter, the Queen's eldest grandson.
When Peter was born he was fifth in line to the British throne, but currently he is 10th in line.
Like his sister Zara, he does not have a royal title and does not carry out any official royal engagements.
As a child, Peter followed in the footsteps of his uncle, Prince Charles, and his grandfather, the Duke of Edinburgh, by being educated at Gordonstoun School in Moray, Scotland.
He graduated with a degree in sports science from the University of Exeter and went on to work for the Jaguar and Williams F1 racing teams.
He left his position as sponsorship accounts manager at Williams F1 in September 2005 when he began work at the Royal Bank of Scotland in Edinburgh.
He is a keen sportsman and played rugby for the Scottish Schools team and still enjoys equestrian sports.
The wedding will be the first royal marriage since that of Prince Charles and the Duchess of Cornwall in April 2005.
A Buckingham Palace spokesman said a date had not been set for the ceremony.