The team represents the IRFU Ulster Branch, which is one of the four primary branches of the IRFU and is responsible for rugby union throughout the geographical Irish province of Ulster, comprising Northern Ireland (Antrim, Armagh, Down, Fermanagh, Londonderry and Tyrone) and three counties in the Republic of Ireland which are Donegal, Monaghan and Cavan.

Prior to professionalisation, Ulster were a representative amateur team taking part in the IRFU Interprovincial Championship.

The two unions amalgamated in 1879, with the provincial branches of Ulster, Leinster and Munster being founded as part of the terms of this arrangement.

Under Cecil Watson, Ulster came third in 1978 and fourth in 1979, and came third in 1980 under Matt Gillen, before form began to return under Willie John McBride, who led them to second place in 1981 and a shared title in 1982.

[10] The Heineken Cup was launched in 1995 to provide a new level of European cross-border competition,[11] and Ulster, coached by Harry Williams and captained by David Humphreys, became the first Irish team to win it in the 1998–99 season, beating beat French side US Colomiers 21–6 in the final at Lansdowne Road in Dublin.

[19][20] Dominant forward play by Australian lock Justin Harrison, New Zealand-born Irish scrum-half Isaac Boss, and a rapid maturing of a youthful home-grown three-quarter line made Ulster champions of the 2005–06 Celtic League.

[23] The team began the 2007-08 season with a poor run of results, and Mark McCall resigned in November following Ulster's embarrassing 32–14 home defeat to Gloucester in the opening round of the 2007–08 Heineken Cup.

[32] For the 2009-10 season a new management structure was put in place, with David Humphreys as director of rugby and Brian McLaughlin as head coach, assisted by Jeremy Davidson and Neil Doak.

[34] The season saw an improvement in Ulster's Heineken Cup form, including their first away win in England against Bath,[35] but they finished eighth in the Celtic League.

Ulster signed key players including 2007 Rugby World Cup winning Springboks Ruan Pienaar[39] and Johann Muller.

[49] New signings for the 2012–13 season included back row forward Nick Williams from the now defunct Aironi,[50] wing Tommy Bowe, returning from his four-year stay at the Ospreys,[51] back row forward Roger Wilson, returning from Northampton Saints,[52] and Irish-qualified South African hooker Rob Herring, initially on a six-month trial.

They finished top of the table in the Pro12, earning a home semi-final, in which they defeated Scarlets 27–16 in the last match before the old grandstand was demolished.

For the first time, Ulster won all their Heineken Cup group games, with away victories against Montpellier and Leicester Tigers being the highlight.

[61] The season ended with the retirements of captain Johann Muller, centre Paddy Wallace, and flanker Stephen Ferris.

Following Humphreys' departure, Mark Anscombe was sacked by the province and was replaced by Ireland defence coach Les Kiss on an interim basis.

[66] New signings included out-half Ian Humphreys, returning from London Irish,[67] lock Franco van der Merwe from the Lions,[68] outside back Louis Ludik from Agen, and flanker Sean Reidy from Counties Manukau.

[72] Before the 2016–17 season, Nick Williams left for Cardiff Blues[73] and Dan Tuohy for Bristol Bears,[74] and Ian Humphreys retired.

[75] Ulster signed back row forward Marcell Coetzee,[76] fullback Charles Piutau[77] and lock Kieran Treadwell.

[82] All-time appearance holder Roger Wilson retired, and scrum-half Ruan Pienaar was blocked by the IRFU from extending his contract.

[84] Before the season started, out-half Paddy Jackson and centre Stuart Olding were charged with rape and suspended from playing pending trial.

[88] After a poor run of form over the Christmas period, Les Kiss resigned as Director of Rugby,[89] and Gibbes cut his contract short, leaving at the end of the season.

[94] Jared Payne, Tommy Bowe, Andrew Trimble and Chris Henry all retired, and Charles Piutau left for Bristol Bears.

[95] Out-half Billy Burns was signed from Gloucester,[96] prop Marty Moore from Wasps,[97] flanker Jordi Murphy from Leinster,[98] and utility back Will Addison from Sale Sharks.

[99] Prop Eric O'Sullivan, wing Robert Baloucoune, centre James Hume, fullback Michael Lowry and flanker Marcus Rea all made their debuts from the academy.

[106] Centre Stewart Moore and wing Ethan McIlroy[107] made their debuts from the academy, and scrum-half John Cooney was Player of the Year for the second time.

[109] Academy players Cormac Izuchukwu, Nathan Doak, David McCann, Callum Reid and Aaron Sexton all made their senior debuts this season.

In the Champions Cup, they made the knockout stage, but went out in a two-legged round of sixteen playoff against Toulouse by an aggregate score of 50–49.

Despite a poor run of results in mid-season,[116] Ulster made the knockout stage of the Champions Cup, going out in the round of 16 to Leinster.

[121] Chief Executive Jonny Petrie left not long after, replaced on an interim basis by Hugh McCaughey.

Out-half Billy Burns left for Munster;[125] prop Steven Kitshoff returned to the Stormers,[126] where he was joined by flanker Dave Ewers;[127] utility back Will Addison signed for Sale Sharks;[128] and centre Luke Marshall retired.