Peter Sullivan scored the decisive try in the added minutes as Ulster edged out Connacht in the opening round of the Rainbow Cup at Kingspan Stadium.
Edinburgh also made a winning start to the competition after they defeated Zebre with a 24-18 margin at Murrayfield Stadium on Friday.
Ulster 24-26 Connacht, Kingspan Stadium
Connacht skipper Paul Boyle started the proceedings with a seventh minute try and Jack Carty kicked the conversion to take them to a seven point lead before Ulster responded back in the 23rd minute with Jacob Stockdale dotting down capitalising on a long pass from John Cooney.
Ulster extended the lead further when Rob Herring touched down at the back of a maul around the half hour mark before Cooney's conversion ensured the teams finished the opening half with a 12-7 scoreline.
The start of the second half saw Connacht reduced to 14-men temporarily with Carty sin-binned for a deliberate knock-on as Billy Burns touched down after good work from James Hume. Cooney missed the conversion but Ulster stretched their lead to 10 points. Despite down on numerical advantage, Connacht fought back through Caolin Blade's try and Tom Daly improved making it 17-14.
Connacht went into the lead at the start of the final quarter as Blade completed his second when he dived from close range and with Daly's conversion the scoreline became 17-21 before replacements Michael Lowry and Dave Shanahan combined with the latter eventually going over in the 72nd minute. Lowry kicked the conversion to make it 24-21. Just when Ulster thought they had the game, Sullivan, with a penalty coming, pounced on a grubber in the added minutes to score the decisive try sealing a thrilling two-point win.
Edinburgh 24-18 Zebre
Carlo Canna started the proceedings with a fourth penalty goal but the response was strong from Edinburgh with Blair Kinghorn feeding Eroni Sau to dive in the corner in the 11th minute and Nathan Chamberlain followed with the conversion making it 7-3. Canna with his second three-pointer in the in the 17th minute reduced the gap before Andrea Lovotti dived in the corner Canna kicked the conversion to make the scoreline 7-13 before the break.
Edinburgh started the second half positively with Sau going past Zebre defenders setting Luke Crosbie over and Chamberlain kicked the extras making it 14-13 and as the final quarter started Matt Currie on his first Edinburgh start dived from close range to take their lead to 21-13. With three minutes left in the game, added a late penalty to extend their lead which proved enough despite a late try for Zebre from Johan Meyer.