The sponsorship deal will kick off from next month when the 2006 competition featuring England, Scotland, Wales, Ireland, France and Italy begins and will run until the 2009 competition.
To mark its continued support, RBS has commissioned the first Triple Crown Trophy, a silver dish that will be given to the team that beats all of the other home nations during this season's tournament. The Six Nations kicks off on February 4 when Ireland play Italy and England take on Wales.
It marks the first time in the Triple Crown's history there will be a permanent memento for either England, Scotland, Wales or Ireland if they beat the other three home nations during the championship.
John Feehan, Six Nations chief executive, said: "To now have something that is tangible and so impressive will add greatly to the already ultra-competitive environment of the RBS Six Nations Championship."
Ireland captain Brian O'Driscoll added: "When we won the Triple Crown in 2004 for the first time in 19 years, it was a fantastic occasion and one of the most memorable days in my career so far, but to have been handed a trophy would have been the icing on the cake."
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