Pro 14 Rugby

Pan-Celtic tournaments were proposed throughout the early professional era, with the creation of the Heineken Cup in 1995 demonstrating that inter-domestic competitions were financially viable. From 1995 onwards, the Welsh Rugby Union (WRU), Scottish Rugby Union (SRU) and Irish Rugby Football Union (IRFU) discussed a number of Celtic league and cup competitions, discussions were also held with the Rugby Football Union (RFU) to form a British & Irish league. These discussions would eventually lead the WRU and the RFU to establish the Anglo-Welsh Cup in 2005, and all four unions to establish the British and Irish Cup in 2009.

The first material steps toward a Celtic league were taken before the 1999–2000 season, when the Scottish districts Edinburgh and Glasgow were formally invited to join the fully professional Welsh Premier Division, creating the Welsh–Scottish League. By 2001, an agreement was made with the Irish Rugby Football Union (IRFU) to bring in the four Irish provinces. The 2001–02 season saw additional matches and a new league structure played alongside the continuing Welsh–Scottish League and the Inter-Provincial Championship in Ireland. The new format was named the Celtic League. The Celtic League had developed by 2005, and the tournament became the sole professional league in Ireland and Scotland (the Anglo-Welsh Cup and semi-pro Welsh Premiership continued in Wales) and had entirely replaced both the Welsh–Scottish League, and the Inter-Provincial Championship.

The first full season of a pan-Celtic competition saw 15 teams compete: the four Irish provinces (Connacht, Leinster, Munster and Ulster), two Scottish teams (Edinburgh Reivers and Glasgow) and all nine Welsh professional teams (Bridgend, Caerphilly, Cardiff RFC, Ebbw Vale, Llanelli, Neath, Newport, Pontypridd and Swansea).

Played alongside each country's own domestic competitions, the teams were split into two groups (of eight and seven) and played a series of round-robin matches with each team playing the other only once. The top four teams from each group proceeded into the knock-out phase until a champion was found. Clashes between teams in the Welsh–Scottish League also counted towards the new competition.

The 2001–02 competition was dominated by the Irish teams with all four sides reaching the last eight, three progressing to the semi-finals, and the thrilling final played at Lansdowne Road contested between Leinster and Munster with Leinster running out 24–20 winners.

Champions Leinster failed to make the quarter-final stage in 2003. In their absence, Munster went on to win the competition by beating Connacht 33–3 in the quarter-finals, Ulster 42–10 in the semi-finals, and Neath 37–17 in the final played in Cardiff.

The format of the Celtic League remained the same for the second season, but saw the addition of a third Scottish district, the newly re-established Scottish Borders. However, the Welsh-Scottish league structure ended permanently in 2002, allowing for the expansion of the Celtic league format in the following season.

A major change in Celtic League came before the start of the 2003–04 season. The Welsh Rugby Union voted to create five new regional sides (Cardiff Blues, Celtic Warriors, Llanelli Scarlets, Neath–Swansea Ospreys and Newport Gwent Dragons). It was agreed that the Celtic League would become the sole professional league of the three countries, incorporating the four Irish, three Scottish and five new Welsh professional teams.

Reformatted into a traditional league competition (double round-robin style, all clubs play each other twice, once home, once away), which meant that a season long 22-round match program was launched, and with a new strength in depth due to the amalgamation of Welsh teams and the continuing strengthening of Irish and Scottish teams through the re-signing and retention of star players, the league has been in rugby terms a success. Also introduced for the 2003–04 season was the Celtic Cup, a straight knock-out cup competition between the 12 Celtic League teams.

However, the unfortunate timing of the league's launch and poor organisation of a working calendar meant that first the 2003 Rugby World Cup and later the Six Nations Championship prevented many of the league's top stars from playing in over half the games. This caused the league to struggle commercially, especially regarding the newly adopted regions in Wales where the game has always traditionally been played on a club basis, not having the regional histories of Ireland or Scotland. The season ended with the Llanelli Scarlets running out as eventual winners, four points ahead of Ulster.

The Welsh Rugby Union controversially purchased and liquidated the Celtic Warriors so that the 2004–05 season saw eleven teams compete in the Celtic League. The new format took the league into what many saw as a make-or-break season,^[] clear of massive distractions such as the Rugby World Cup. With the Welsh regions partly embedded, the signs were that the Celtic League would be a competition that could continue. It was suggested that Italian sides might join an expanded Celtic League, an idea that eventually happened in 2010.

The league format was further refined at the end of the 2003–04 season, with the participants better managing the dates of the matches so as to not interfere with the national squad set-ups and to make the league more commercially viable. The league was played until April, and then the Celtic Cup was contested among the top eight teams.

The 2004–05 season was the first season that Ireland agreed to use the Celtic League standings to determine which provinces would enter the Heineken Cup. The IRFU had previously classed Connacht as a "development" team and so nominated Leinster, Munster and Ulster over Connacht. The IRFU also insisted on International squad training sessions taking precedence over Celtic League matches, with Irish provinces (especially Munster and Leinster) occasionally fielding virtual second teams for Celtic League games. Some claimed this had the effect of devaluing the competition. However, despite this approach, Munster finished second and Leinster third, with Munster winning the Celtic Cup. The Ospreys topped the league table, making it two in a row for Welsh regional sides.

In 2005, there were discussions over a potential Anglo-Welsh Cup competition which some saw as undermining the Celtic League. Despite Welsh assurances that the proposed Anglo-Welsh tournament would not interfere with their commitments to either the Celtic League in its present format or an expanded 'Rainbow League', the WRU made arrangements to play games on five weekends that clashed with Celtic League fixtures. The SRU and IRFU then threatened to expel the Welsh sides from the Celtic League in June 2005. It was proposed that the competition would continue as a Scottish and Irish affair for the 2005–06 season, with the possible addition of four Italian sides and the re-admittance of Welsh sides for the 2006–07 season. However a deal was reached that allowed for the Celtic League to continue with the Anglo-Welsh cup fixtures involving Welsh clubs rescheduled.

Despite these problems, the league enjoyed its most successful season, with the record attendance at a Celtic League match being broken four times, from 12,436 at the match between the Cardiff Blues and the Newport Gwent Dragons in December to 15,327 for the match between the Cardiff Blues and Leinster at the Millennium Stadium. The total attendances for the season were up nearly 50,000 at 571,331 compared to 521,449 for the previous season.

The league went down to the last round with Ulster and Leinster both in contention. Following Leinster's victory over Edinburgh and with Ulster losing against the Ospreys, it looked like the cup would go to Dublin but David Humphreys kicked a last-minute drop goal from 40 metres to clinch the game and the league for Ulster.

In May 2006, Magners Irish Cider were named as the competition sponsors for the next five seasons, and the league was renamed as the Magners League. Although known as Bulmers Irish Cider in the Republic of Ireland, the Magners brand name was used there for the league. The sponsorship followed on from Magners' previous sponsorship deals with Edinburgh and the London Wasps.

The Scottish Rugby Union announced that the Borders territory would be disbanded from the end of the 2006–07 season. It may be revived when the Scottish Rugby Union debt decreases enough to make it financially viable along with a possible fourth Scottish territory (four professional teams being the original plan for the SRU) with Falkirk, Stirling or a London-based team being possible locations; or even the Caledonia Reds, the forgotten Scottish region. In the meantime Scotland would have only two professional teams based in Edinburgh and Glasgow.

The league's record attendance was smashed in this season with a full house at Lansdowne Road (48,000) for Leinster v Ulster. This was the last game in the stadium prior to its demolition, and was billed as "The Last Stand".

The league was won by the Ospreys on the final day of fixtures. The Blues' home win over Leinster allowed the Ospreys to top the league by a single point and take the title with an away win at Borders.

Only ten teams competed in the 2007–08 season, after the Borders were disbanded at the end of the 2006–07 season. Glasgow Warriors moved their home games to Firhill. After missing out on the title on the last day for the previous two seasons, Leinster finally won the 2007–08 title with one game remaining. They had been runaway leaders for much of the season.

In April 2008 it was announced that the Celtic League was to introduce a play-off system commencing in the 2009–10 season to determine the winner, thus generating a greater climax to the season and bringing it in line with other major leagues such as the English Premiership and French Top 14.

The 2008–09 season was decided quite early in the season as Munster claimed the title without playing, as they were preparing for their Heineken Cup semi-final against Leinster. The final challenge from Ospreys was snuffed out when the Dragons denied them a bonus point win on 30 April. Munster had led pretty much from the start of the season with a team largely captained by Mick O'Driscoll showing Munster's squad depth. Munster lost only four games, three to the other Irish teams, including a double loss to Ulster. Felipe Contepomi finished as league top scorer for Leinster, the year they went on to win the Heineken Cup.

The 2009–10 season was the last 10-team league as the Italian teams joined in 2010–11. The league was one of the most competitive in years with perennial wooden-spooners Connacht challenging Ulster all the way for the third Irish Heineken Cup spot. Ulster needed a superb away bonus point win at Edinburgh to seal it, ending Edinburgh's own play-off hopes. Scarlets had a disappointing campaign as typical Welsh underdogs the Dragons had a great season, eventually finishing mid table and comfortably qualifying for the Heineken Cup. Luckily for the Scarlets, Cardiff Blues won the Amlin Cup and thereby earned Wales an extra Heineken Cup place. 2009–10 was also the first time a play-off was used to decide the champion, previously the top team at the end of the season was champion. The Scottish teams and particularly Glasgow came of age and had a fine season, finishing third in the end.

The four qualifiers for the play-offs were Leinster, Ospreys, Glasgow and Munster in that order, each country having at least one team. In the semi-finals Leinster defeated Munster at the RDS, after Ospreys overcame Glasgow in Swansea. In the 2010 Celtic League Grand Final at the RDS in Dublin the Ospreys shocked Leinster, winning the title 17–12 with their first win in Dublin in five years.

The 2010–11 saw the introduction of the two Italian sides, Aironi and Benetton Treviso. In the new 12 team format, the play-offs came down to Munster hosting the Ospreys in one semi-final, and Leinster hosting Ulster in the other.

The two home sides went on to win their respective matches and the final was held in Thomond Park, home of Munster rugby, where they defeated Leinster (who had just been crowned champions of Europe a week earlier).

The 2011–12 season saw a re-branding of the competition as the RaboDirect Pro12. Leinster were the runaway winners of the regular season, with a 10-point cushion over the Ospreys in second. The top four were Leinster, Ospreys, Munster and Warriors in that order. Ospreys easily overcame Munster at home in the first semi-final in Swansea while Leinster beat the Glasgow Warriors in the RDS after giving up a strong lead. In the final, also held at the RDS, Leinster were aiming to become the first Celtic League team to complete a domestic and European double, after beating Ulster the previous week in the Heineken Cup final. After trailing for most of the game, Ospreys took a late lead through a try by Shane Williams. Dan Biggar then landed a difficult conversion to give Ospreys their fourth title by a single point, 31–30.

After two years in the competition Aironi played their final match, as their licence to compete was revoked by the FIR for financial reasons.

With the demise of Aironi they were replaced with a new FIR controlled team to be based in Parma called Zebre, near the Aironi base in Viadana. The Welsh clubs chose to operate under a new self-imposed salary cap, which led to a number of departures from the Welsh teams as they strove to balance their books. Some high-profile Welsh players moved to the French Top 14, but other Pro12 teams also benefited with the likes of Casey Laulala going to Munster from Cardiff Blues, Sean Lamont to Glasgow from Scarlets, Dan Parks from Cardiff Blues to Connacht and Tommy Bowe from Ospreys back to Ulster.

Ulster topped the table in the regular season, with Leinster, Glasgow and Scarlets completing the top 4 in that order. They then went on to comfortably beat Scarlets 28–17 in Belfast, while Leinster were hard pressed by Glasgow in a tense 17–15 win for the hosts. In the final (held in the R.D.S. due to redevelopment of Ravenhill) Leinster prevailed 24–18 to win their 3rd title.

Rabo Direct announced that this was to be their last season as sponsors. This, combined with the ongoing uncertainty surrounding the future of the European Cup, meant that there were concerns over the future commercial viability of the tournament. However, despite all off-field issues it was a successful season with a new high for both total attendance and for a single game (51,700 for Leinster v Munster).

In the end Leinster topped the table, having led for most of the season. Glasgow had a late surge to finish 2nd overtaking Munster and Ulster in the process. All four teams showed they were worthy contenders in the next round with Leinster needing to score a late try to beat Ulster 13–9 in Dublin while Glasgow just got past Munster in Scotstoun by one point to win 16–15. The final in the R.D.S. was also a close game for most of the match with Leinster forced to defend for long periods. However they eventually pulled clear, adding two late scores which made the final result look somewhat lopsided at 34–12.

The RaboDirect title sponsor was replaced by Guinness. With the Heineken Cup being replaced by the 20-team European Rugby Champions Cup in the 2014–15 season, the Pro12 table had a greater impact on qualification. Under the previous format, the Pro12 provided a minimum of 10 teams, with Scotland and Italy providing two teams each, and Ireland and Wales both providing three. The new system saw a total of seven teams, with one place now being reserved for the highest-finishing Pro12 team from each of four participating countries and three other qualifiers based solely on league position. The other teams were entered in the new second-tier competition, the European Rugby Challenge Cup.

Leinster were the defending champions having beaten Glasgow Warriors in the previous season's playoff final, to become the first team in the league to successfully retain the trophy. Leinster were unable to defend their title as they failed to qualify for the end-of-season playoffs for the top four teams after the regular season. Glasgow Warriors finished the regular season on top of the table, and were crowned champions for the first time, beating second seeded team Munster 31–13 in the final. Thus, the Warriors became the first Scottish team to win a professional trophy, beating Edinburgh's appearance in the final of the 2014–15 European Rugby Challenge Cup.

With the 2015 Rugby World Cup taking place during the opening months of the season, changes were made to the usual fixture schedule to minimise the effect on teams who released players to take part. The low number of games in the opening weeks of the season led to fixture congestion at the end of the tournament, with each team playing a game every weekend for 16 weeks straight from October 2015 to January 2016, including European matches.

As in the previous season, qualification to the European Champions Cup was guaranteed to the top team from each country participating in the league, with the three highest placed team's not already qualified also earning a berth. Unlike in the previous season where the 20th tournament spot was decided by a play-off involving teams from the Pro12, France's Top 14 and the English Premiership, due to fixture congestion from the World Cup, the final spot in the tournament was reserved for the winner of the 2015 European Challenge Cup if not already qualified.

The delayed start to the season, and absence of established international players during international Test and Six Nations windows, arguably gave some advantage to 'lesser' teams, and Connacht, coached by Pat Lam, duly led the league for much of the season. Despite not ultimately finishing top of the league, they converted their form into a maiden championship title in the post-league play-off matches, including a home semi-final victory over reigning champions Glasgow Warriors, and the Pro12 Final against league-topping Leinster at the neutral venue of Murrayfield Stadium in Edinburgh.

Despite losing their first three matches, the Scarlets finished third in the league. They became the first team in the Pro 12's history to win an away semi-final, beating Leinster 27–15 at the RDS Arena, before beating league-topping Munster 46–22 at the Aviva Stadium. Scarlets wing Steff Evans ended up as the league's top try scorer with 11 tries.

Big changes happened this season with the addition of two South African teams and a change from a league format of home and away to a conference structure championship. The 14 teams were split into two conferences of seven teams each. They play each team in their own conference twice (12 games) and each team in the other conference once (7 games), plus two derby games against the team(s) in the other conference from their own country, making 21 matches in total. The team that finishes top in each conference qualifies directly, one for each of the semi-finals, while the teams that finish second and third in each conference qualify as the four quarter-finalists to determine the other two semi-finalists.

Leinster would regain the title at the Aviva Stadium in Dublin and would become the first Pro14 side to ever win a European and Domestic double, they did so by beating previous holders Scarlets in a high scoring affair, 40-32. The two sides had already met in the European Semi-Final only a few weeks prior to the playoff final in very similar circumstances, at the same stadium and with much of the same lineup either side. It was Leinsters fifth domestic title.

The two conference format continued this season. The top three eligible European teams in each conference automatically qualified for following year's Champions Cup. The fourth ranked eligible team in each conference met in a play-off match with the winner taking the seventh Champions Cup place. As Leinster lost the Champions Cup final on 11 May 2019, Ospreys hosted Scarlets in the play-off on 18 May 2019. Ospreys secured the sole Wales Champions Cup place for following season by defeating Scarlets 21-10. The Pro14 final was played between Glasgow Warriors and Leinster and was played at Celtic Park in Glasgow. Leinster won the game 18–15 to retain the title.

All teams played their normal schedule until round 13 after which an additional two rounds of derby matches were played by the 12 European teams. The Southern Kings announced in August 2020 that they had voluntarily withdrawn from the league for the remainder of 2020. The top four eligible European teams in both conferences automatically qualify for the 2020–21 European Rugby Champions Cup. (The South African teams did not compete in the Champions Cup.) Qualification was based on league position after round 13. The grand final match was due to be held at Cardiff City Stadium, however, on 19 March 2020, Celtic Rugby DAC cancelled the event due to the COVID-19 pandemic. The re-arranged match took place on 12 September 2020 at the Aviva Stadium between defending champions Leinster and Ulster. Leinster won the match 27–5 to defend their title and complete a hat-trick of title wins.

Twelve teams competed in this season — four Irish teams: Connacht, Leinster, Munster and Ulster; two Italian teams: Benetton and Zebre; two Scottish teams: Edinburgh and Glasgow Warriors; and four Welsh teams: Cardiff Blues, Dragons, Ospreys and Scarlets. Neither of the two South African teams competed this season, with the Cheetahs unable to compete due to the COVID-19 pandemic, and the Southern Kings having entered into voluntary liquidation due to heavy financial losses.

Due to the delays experienced during the 2019–20 season as a result of the COVID-19 pandemic, the 2020–21 season started later than usual on 2 October 2020. Leinster won their fourth consecutive Pro14 title and 8th overall defeating Munster in the grand final on 27 March.

The 2020–21 Pro14 was reduced to twelve teams as the two South African teams - the Cheetahs and Southern Kings - were not allowed to travel internationally in 2020 due to the COVID-19 pandemic. In September 2020, the Southern Kings ceased operations and the South African Rugby Union council began exploring the possibility of the four South African former Super Rugby teams - the Bulls, Lions, Sharks and Stormers - joining an expanded Pro14. PRO14 Rugby announced in December 2020 that the 2020–21 Pro14 regular season would conclude after 16 rounds, and the top team from each conference would advance to a final in March 2021. The Pro14 Rainbow Cup then commenced in April and introduced the four new South African teams. The first-placed teams from each tournament, Benetton and Bulls, played in the final in Treviso. Benetton won 35–8 in front of their home crowd for a historic first win of an international competition for any Italian club.

The tournament consisted of 18 rounds. There were four regional pools: The Irish Shield pool (featuring the four Irish teams), the Welsh Shield pool (featuring the four Welsh teams), the South African Shield pool (featuring the four South African teams) and the Scottish/Italian 'Azzurri/Blue' Shield pool (featuring the two Italian and two Scottish sides). Teams play six matches against their regional pool rivals home and away. The remaining twelve matches are made up by a single round robin, consisting of an even number of six home and six away matches against all the sides from the other pools.

The first United Rugby Championship Final was an all-South African derby, ensuring the first ever South African winner of the tournament, the Bulls having narrowly missed out on winning the transitional Pro14 Rainbow Cup competition. It also marked the first time in the history of the competition that a Grand final play-off match has not included at least one Irish province, a run of 14 finals. The Stormers defeated the Bulls 18–13 in Cape Town.

The tournament consisted of 21 rounds; 18 rounds of regular season play, followed by three rounds of play-offs. The final, held on 27 May 2023, saw Munster defeat defending champions the Stormers by a score of 19–14.