The Irish Rugby Football Union (IRFU) (Irish: Cumann Rugbaí na hÉireann) is the body managing rugby union in Ireland. The IRFU has its head office at 10/12 Lansdowne Road and home ground at Aviva Stadium, where Irish rugby union international matches are played. In addition, the Union also owns Ravenhill in Belfast, Thomond Park in Limerick and a number of grounds in provincial areas that have been rented to clubs.

Initially, there were two unions both founded in 1874 – the Irish Football Union had jurisdiction over clubs in Leinster, Munster and parts of Ulster; the Northern Football Union of Ireland controlled the Belfast area. The IRFU was formed in 1879 as an amalgamation of these two organisations and branches of the new IRFU were formed in Leinster, Munster and Ulster. The Connacht Branch was formed in 1900.

The IRFU was a founding member of the International Rugby Board in 1886 with Scotland and Wales. (England refused to join until 1890).

Following the political partition of Ireland into separate national states, the Republic of Ireland (originally the Irish Free State then Éire) and Northern Ireland (a political division of the United Kingdom), the then Committee of the Irish Rugby Football Union decided that it would continue to administer its affairs on the basis of the full 32 Irish counties and the traditional four provinces of Ireland: Leinster (12 counties), Ulster (9 counties), Munster (6 counties), and Connacht (5 counties).

The Rugby Football Union (RFU) was founded in 1871 as the governing body for the sport of rugby union, and performed as the international governing body prior to the formation of the International Rugby Board (IRB) in 1886. It has since functioned within England as a society to promote and run the sport, including organising international matches for the England national team, educating and training players and officials and acting as the governing body for England.

The RFU is structured as an industrial and provident society, owned by over 2,000 member clubs, representing over 2.5 million registered players, and forms the largest rugby union society in the world, and one of the largest sports organisations in England. It is based at Twickenham Stadium, London.

In September 2010 the women's rugby body the Rugby Football Union for Women (RFUW) was integrated into the RFU as a "constituent body", and whilst it retains some independence within the organisation, its adoption of RFU structures and management effectively unify the men's and women's sport under a single governing body.

Rugby union is a popular team sport played in Ireland. The sport is organised on an all-Ireland basis with one team, governing body and league for both the Republic of Ireland and Northern Ireland. Ireland is the third-oldest rugby nation after England and Scotland respectively, and the game was organised there fractionally before in Wales.^{[citation needed]}

The Irish Rugby Football Union (IRFU) is the governing body for rugby union in Ireland. The IRFU is divided into five branches. The four main branches represent the four provinces of Ireland: Ulster, Munster, Leinster and Connacht. Each provincial branch organises the sport within its geographic area. All four field senior teams that compete in the Pro12 (historically the Celtic League), and all except Connacht field "A" teams in the semi-professional British and Irish Cup. The fifth branch is the Exiles Branch, tasked with identifying and developing players living in England, Scotland and Wales who are qualified to represent Ireland through their ancestry.

The Ireland national rugby union team represents the island of Ireland (both Republic of Ireland and Northern Ireland) in rugby union. The team competes annually in the Six Nations Championship (which they have won eleven times outright and shared eight times) and every four years in the Rugby World Cup, where they reached the quarter-final stage in all but two competitions (1999 and 2007). Ireland is also one of the four unions that make up the British and Irish Lions – players eligible to play for Ireland are also eligible for the Lions. Eight former Ireland players have earned induction into the International Rugby Hall of Fame, with five of them also having earned induction into the IRB Hall of Fame.

Outside centre Brian O'Driscoll, the current captain and Ireland's current all-time leader in tries, is considered one of the best rugby players in the world and led Ireland to only their second Grand Slam in March 2009. He was also captain of the Lions on their 2005 tour of New Zealand, although his on-field captaincy was cut short by a controversial injury in the Lions' first Test. O'Driscoll was succeeded as Lions captain for their 2009 tour of South Africa by his current teammate, lock Paul O'Connell. Keith Wood, O'Driscoll's predecessor as Ireland captain before retiring in 2003, was the inaugural IRB International Player of the Year in 2001.

Brian Gerald O'Driscoll (born 21 January 1979) is an Irish professional rugby union player. He is the current captain of the Ireland Rugby team and captained Leinster Rugby until the start of 2008 season. He also captained the British and Irish Lions for their 2005 tour of New Zealand. Registered at University College Dublin RFC, he plays at outside centre for the Irish provincial team Leinster. O'Driscoll was chosen as Player of the Tournament in the 2006, 2007 and 2009 RBS Six Nations Championships.

O'Driscoll has 123 Test caps, 117 for Ireland (80 as captain), and 6 for the British and Irish Lions. He has scored 45 tries for Ireland and 1 try for the Lions in 2001, making him the highest try scorer of all time in Irish Rugby. He is 8th-highest try scorer in rugby union history, and the highest scoring centre of all time. O'Driscoll holds the Six Nations record for most tries scored with 25. He has scored the most Heineken Cup tries (30) for an Irishman. He is widely regarded as one of the best centres to have played the game.