Connacht secured second spot, and a home semi-final, after they beat Glasgow 14-7 at the Sportsground on Saturday.
It was a game of few chances, with Bundee Aki'’s try separating the sides at half time in miserable conditions.
From the restart, Gordon Reid levelled the scores, but the visitors’ resurgence was hampered when prop Sila Puafisi was sent off for leading with his head in the ruck.
Tiernan O’Halloran’'s try on his 100th appearance won it for the hosts, who finished the season in second, leaving pre-match favourites Glasgow third, one point behind Connacht. The two sides will now meet again in the semi-finals.
Connacht broke first through Aki, who did well to avoid a couple of challenges, before going over at the base of the posts. AJ MacGinty’'s conversion was simple.
That was how it finished in the first half, but Glasgow showed fight at the start of the second period, with Gordon Reid going over from close range following a lineout. Finn Russell, who had struggled previously on the day with his kicking, levelled the scores.
Just minutes later, Puafisi led with head in the ruck, leaving referee Ian Davies with no choice but to dismiss the prop as contact was made with Connacht scrum-half Kieran Marmion.
That dismissal was taken full advantage of by the hosts, with O’'Halloran beating Stuart Hogg for pace to reach a grubber kick from Shane O’'Leary, who converted.
Connacht held on for the well-deserved victory to round off a successful regular season.
Tries: Aki, O'Halloran
Cons: MacGinty, O'Leary
Red Card: Puafisi
Connacht: 15 Tiernan O’Halloran, 14 Nidi Adeolokun, 13 Robbie Henshaw, 12 Bundee Aki, 11 Matt Healy, 10 AJ MacGinty, 9 Kieran Marmion, 8 John Muldoon (c), 7 Jake Heenan, 6 Sean O’Brien, 5 Aly Muldowney, 4 Ultan Dillane, 3 Finlay Bealham, 2 Tom McCartney, 1 Ronan Loughney
Replacements: 16 Dave Heffernan, 17 JP Cooney, 18 Rodney Ah You, 19 Quinn Roux, 20 Eoin McKeon, 21 John Cooney, 22 Shane O’Leary, 23 Peter Robb
Glasgow: 15 Stuart Hogg, 14 Tommy Seymour, 13 Alex Dunbar, 12 Peter Horne, 11 Lee Jones, 10 Finn Russell, 9 Ali Price, 8 Josh Strauss, 7 Ryan Wilson, 6 Rob Harley, 5 Jonny Gray (c), 4 Leone Nakarawa, 3 Sila Puafisi, 2 Fraser Brown, 1 Gordon Reid
Replacements: 16 Pat MacArthur, 17 Jerry Yanuyanutawa, 18 Zander Fagerson, 19 Tim Swinson, 20 Simone Favart, 21 Grayson Hart, 22 Mark Bennett, 23 Sean Lamont
Referee: Ian Davies (Wales)