The Ireland rugby union team represents both the Republic of Ireland and Northern Ireland in rugby union, a popular sport throughout Ireland although the dominant one only in limited geographical areas. Ireland compete annually in the Six Nations Championship (which they have won ten times outright and of which they have shared the championship eight times) and in the Rugby World Cup every four years where they have been eliminated at the quarter-final stage in all but one competition. They also form a quarter of the British and Irish Lions. Eight former Ireland players have earned induction into the International Rugby Hall of Fame.

Historically, Ireland have been the least successful of the rugby union home nations, with the fewest number of Six Nations Championships (10) and Grand Slams (one). Ireland have also been regular winners of the wooden spoon in the Six Nations Championship and its predecessor tournaments. However, Irish rugby union is widely acknowledged to have made the transition to professionalism more successfully than other middle-ranking rugby powers (such as Wales and Scotland) and Ireland have produced good results, especially for a nation with a population of only six million (when combining the Republic of Ireland and the Northern Ireland) with strong competition for players with Gaelic games and soccer. They have won three Triple Crowns in the last four years. Outside centre Brian O'Driscoll, the current captain and Ireland's current all-time leading try scorer, is frequently named as one of the finest rugby players in the world. Other world class players on the side include centre Gordon D'Arcy; eight, Denis Leamy; lock, Paul O'Connell; out half and all-time leading Ireland points scorer Ronan O'Gara; and back row forward, David Wallace. In the recent past, Keith Wood, O'Driscoll's predecessor as Ireland captain before retiring in 2003, was the inaugural IRB International Player of the Year in 2001.

After their 2006 Autumn internationals match against Australia, Ireland climbed to third in the world on the International Rugby Board (IRB) World Rankings; a position they had not seen since the ratings began in 2003. Despite remaining unbeaten in the end of year Tests, they dropped to fifth in the world rankings, before rising to fourth after their opening 2007 Six Nations victory over Wales, but have recently dropped back to fifth after the 2007 Six Nations defeat to France but bounced back in their follow up match against England with a record 43-13 victory. They recently won the 2007 Triple Crown trophy narrowly defeating Scotland 19-18 in Murrayfield, and lost the 2007 Six Nations Championship to France when Elvis Vermeulen of Les Bleus was awarded a try by the Irish television match official at the death against that gave them the championship on points difference. Ireland performed well below par in the 2007 World Cup. They were knocked out in the pool stages after losing to Argentina.