Prince William is to become the Vice Royal Patron of the Welsh Rugby Union.
Prince Williams is a keen rugby and football fan
He will take up the position from February next year in time for the 2007 Six Nations tournament.
The prince said he was "honoured" to take on the role.
"Rugby is such a central part of Welsh life and I hope to be able to contribute in some way to the development of the sport, both at the community level and on the international stage," he added.
Prince William, who is also a president for the FA, is currently undergoing officer training at Sandhurst.
His new role will be the fourth for the prince - he is president of England's Football Association (FA) as well as patron of the homeless charity Centrepoint and the conservation charity the Tusk Trust.
WRU chairman David Pickering said he was delighted Prince William is to become the new Vice Royal Patron.
He said: "Rugby truly is our national sport in Wales, and the prince's passion for and commitment to the game is well-known.
"I saw his tremendous ambassadorial qualities first-hand during the British and Irish Lions tour last summer and during his visit to Cardiff for the FA Cup Final in May.
"He has particular qualities when it comes to interacting with young people and I am sure he will prove inspirational in his new role within Welsh rugby. We're all thrilled."
In 2003, the prince attended a reception, hosted by the Queen for England's World Cup rugby players at Buckingham Palace.