The centre-half agreed the deal on Friday - his 29th birthday - and it will come as a welcome boost after being ruled out of the FA Cup final at Wembley with a knee injury.
Chief executive Peter Kenyon said: "We are delighted that Riccy has committed himself to us for the next five years. He has been a key player for us since he joined and has been in fantastic form this season. Without doubt he is one of the best central defenders in the world."
© Copyright PA Sport Ltd 2007, All Rights Reserved.