The 2005 RBS 6 Nations Championship was the sixth series of the Six Nations Championship to be held since the competition expanded in 2000 to include Italy. Including the previous incarnations as the Home Nations and Five Nations, this was the 111th series of the northern hemisphere rugby union championship.
Unlike most contemporary rugby union competitions, the 2005 Six Nations did not use a bonus point system. Match winners receive two points, with one for a draw and none for a loss. The first tiebreaker is point differential.
In this year, Wales won the Grand Slam, becoming the first team ever to win a Grand Slam playing more games away than at home.