Leinster

The Leinster Branch was inaugurated at a meeting on 31 October 1879. The meeting was held at Lawrence's premises at 63 Grafton Street and was largely attended. Although this was the formal founding of Leinster as we know it today, with the amalgamation of the Irish Football Union and the Northern Union, the Leinster provincial team had been active since 1879 – when the first interprovincial derby was played against Ulster. The Leinster and Ulster teams also made up the representative Irish team that competed against England in Ireland's first-ever international in 1875. Upon the founding of the union, Munster were also added to the fray in 1879, when their first provincial team was selected and first Munster players represented Ireland.

F. Kennedy (Wanderers) was elected first Hon. Secretary of the Branch and C.B. Croker (Lansdowne) first Hon. Treasurer.

The function of the Branch was to organise the game of rugby football in the province. Every year five representatives would be selected to join the IRFU Committee. They would be known as the "Leinster Five" and would pick the Leinster representative teams.

The first Interprovincial matches between Leinster, Ulster and Munster were held in 1875. At this time the matches were played with 20 players a side. Leinster lost to Ulster by a converted try and beat Munster by one goal to nil. Since then there has been a match between these teams annually, with Connacht joining the fold in 1885.

Leinster Schools Interprovincial matches have been taking place since 1888. Leinster Schools beat the Ulster Schools in Belfast on Saturday 7 April by a dropped goal to a try. Their first match against Munster Schools took place on 18 March 1899, when Leinster won by two tries to one.

The early 1920s led to the creation of the Provincial Towns Cup and the Metropolitan Cup, which are still hard-fought competitions in the Leinster Rugby calendar. Much has changed in rugby over the years, but the original idea of Leinster Club Rugby acting as a feeder for the Leinster Interprovincial side, though now professional, still stands true.

All Interprovincial matches were abandoned during the years of the Great War (1914–1918) and the War period (1939–1945), though unofficial matches were played.

The first major touring side to play Leinster was a team drawn from the New Zealand Army – the Kiwis, in 1946. Although it was not an official touring side organised by the New Zealand Rugby Union, the quality of the match, which was drawn 10 points each, is still remembered to this day.

The first official overseas touring side that came to play Leinster was an Australian touring side in 1957. Since then, Leinster has played against every major touring side from Fiji to France.

Before the days of professional rugby union, there was further emphasis on Irish club rugby as opposed to the provincial game. During these times the provincial sides were purely representative sides and games were far less frequent than now. Between 1946 and 2002 the sides would meet annually to contest the Irish Interprovincial Championship and on rare occasions would be tested against touring international sides. When rugby union was declared 'open' in 1995, these four teams became the four professional teams run by the Irish Rugby Football Union and therefore much of the history of the side has been made in the modern era.

Leinster became a professional outfit in the mid-1990s. The "Leinster Lions" name came into existence during the 2001–02 season as the result of a joint marketing initiative between Leinster Rugby and its kit sponsors, the Canterbury Clothing Company. Before the start of the 2004–05 season, the 'Lions' was dropped from the name. It is still used for marketing and branding, in particular, the Cubs Club for Junior members of Leinster Rugby. The Leinster mascot is "Leo the Lion". It was also during this time that the song “Molly Malone” became a match fixture to be sung by the fans.

Leinster's first season in the newly formed Celtic League ended in success as the Lions were crowned the inaugural champions, beating rivals Munster Rugby in the 2001–02 final. In 2002–03, they became only the third team in the history of the European Cup to win all their games in pool play. They also went one step further in the playoffs than the previous season by reaching the semi-finals (for the first time since 1995–96), but lost at home against French side Perpignan, which was accompanied by an unsuccessful season in the Celtic League. The 2003–04 season also ended in disappointment as Leinster slumped to their worst ever league performance and failed to qualify from their European Cup group.

Leinster improved during the 2004–05 season, finishing 3rd, just three points behind the eventual winners, the Ospreys. Leinster also won all of their pool games in that year's European Cup, and were again among the favourites for the title, however they went out at the quarter final stage to Leicester Tigers.

The next two seasons of the Celtic League were to end in near misses for Leinster, as they lost out on the 2005–06 and 2006–07 league titles on the final day of the season. These seasons also saw progress in the European Cup. In 2005–06, Leinster progressed to the semi-final but were eliminated by Irish rivals Munster at Lansdowne Road and they reached the quarter-final the following year where they were beaten by eventual winners London Wasps.

Increasing attendances at Leinster games led to a move across Dublin 4 from Donnybrook Stadium to the redeveloped RDS Arena.

In 2007–08, Leinster failed to qualify from their European Cup pool, but did end the season as Celtic League champions, sealing the title with a 41–8 victory over the Newport Gwent Dragons in front of their home fans at the RDS.

In the 2008–09 season, Leinster topped their European Cup pool despite away losses to French side Castres and English side Wasps. Victory over Harlequins in the quarter-finals followed, despite the Bloodgate Scandal. Leinster overcame Munster 25–6 in a semi-final in Dublin's Croke Park that broke the world record attendance for a club rugby union game with a crowd of over 82,200. Leinster won the 2009 European Cup Final in Murrayfield Stadium in Edinburgh, beating Leicester Tigers 19–16 to claim their first European crown.

In 2009–10 Leinster was eliminated from the European Cup at the semi-final stage by eventual winners Toulouse. Also despite having topped the Pro12 league during the regular season, Leinster lost the first-ever Play-off Final 17–12 on their home ground to the Ospreys.

In the 2010–11 European Cup, Leinster defeated the top English teams (Leicester Tigers, Saracens & Northampton Saints), as well as top French sides, Toulouse (who were the defending European champions), Racing Metro & Clermont Auvergne, (the French Champions). to go on to regain their title as champions of Europe in the 2011 European Cup Final at the Millennium Stadium in Cardiff. Trailing at half time, Leinster scored 27 unanswered points in the second half to beat Northampton 33–22 and claim their second European crown with the biggest comeback in European Cup final history. Leinster were also chasing a Pro12 & European Cup double, but lost 19–9 to Irish rivals Munster in the Pro12 Final.

In 2011–12 Leinster became only the second side ever to retain the title of European Champions. Leinster emerged unbeaten in group play to top their group and went on to defeat the Cardiff Blues 34–3 in the quarterfinals, followed by a 19–15 semifinal victory over ASM Clermont Auvergne. and defeated Ulster in the first all-Irish final 42–14, recording the most points scored and the most tries scored in a European Cup final as well as becoming the first unbeaten side to win the European Cup. Once again, Leinster targeted the double, and faced a repeat of the 2010 Pro12 final against the Ospreys. Leinster's domestic title challenge fell at the final hurdle, conceding a final minute try to slump to a one-point defeat, and unable to complete the double despite topping the table in the regular season.

The 2012–13 campaign proved to be another successful season for Leinster Rugby. The club finished in second place during the regular season of the Pro12 and defeated Glasgow Warriors by a score of 17–15 in their semi-final play-off match on 11 May 2013. On 17 May, Leinster were crowned champions of the European Challenge Cup after defeating Stade Français 34–13 in the final at their home ground, the RDS Arena. Leinster successfully completed the double on 25 May, defeating Ulster 24–18 in the Pro12 final to claim their third league championship.

Leinster continued their success in the 2013–14 season by becoming the first team ever to defend the Pro12 title, topping the league in the regular season and defeating Glasgow Warriors 34–12 in their fifth consecutive Pro12 play-off final and also secured their seventh major title in as many years.

Following a remarkable run of seven major trophies in seven years, Leinster's title run came to an end following the 2013–14 season. The 2014–15 season saw a dip in form, with Leinster finishing in fifth place in the league and failing to make the play-offs. Fortunes in the newly formed Champions Cup were better, with the team reaching the semi-final where they were defeated in extra-time by eventual winners, Toulon. At the end of the season, head coach Matt O'Connor left the club by mutual consent with former club captain, Leo Cullen, being named as his replacement. Cullen then brought in ex-England coach Stuart Lancaster as senior coach at the start of the 2016–17 season, which saw a huge improvement from Leinster as well a big group of young players coming through. Despite playing brilliant rugby all season, Leinster failed to win any silverware, falling short in the Champions Cup semi-final to old rivals Clermont and shocked by the Scarlets in the Pro12 Semi-Final at the RDS. However, there was huge optimism amongst the players and supporters as they believed this was only the start of a new generation and perhaps another era of success.

Starting with the 2017–18 season, Leinster won four straight Pro14 championships. In Europe, they won the 2017-18 Heineken Cup, defeating Racing 92 by a score of 15–12 in the final in Bilbao. They were runners-ups four times in 2018-19 Heineken Cup, 2021-22 Heineken Cup, 2022-23 Heineken Cup and the 2023-24 Heineken Cup. Leinster were knocked out of the Heineken cup competition in the quarter-finals in 2019–20, and again at the semi-finals stage in 2020–21.

The format of the 2021–22 competition was affected by the COVID-19 pandemic. Leinster won their first round matchup with Bath. However, the day prior to Leinster's second match, an away fixture to Montpellier, the EPCR announced that the match would not go ahead, and instead awarded a 28–0 win to Montpellier. This was despite Leinster having a full squad certified to be COVID-free, named, and ready to travel. The following day, the EPCR announced that all other matches involving French and UK teams from the same second round would be postponed to a future date. Following the EPCR's decision to award Montpellier a 28–0 bonus-point win for their cancelled round two clash, Leinster beat Montpellier by 89–7, with the 82 point margin eclipsing their previous biggest win in Europe set against Bourgoin back in 2004.