Leinster fell to their first defeat in 27 matches as Connacht produced a rousing display to run out victors at the RDS.
A total of 616 days have passed since the reigning PRO14 champions last tasted defeat but their armour was cracked by a standout performance by Connacht fly-half Jack Carty.
Two tries from Carty and one for both Alex Wootton and Tom Daly helped to give Connacht a 11-point winning margin, complemented by Carty's haul of 15 points off the kicking tee.
This week had seen doubts overshadow the match after Connacht announced a ‘number of players' had tested positive for Covid-19. While Leinster themselves had recorded two cases.
But the game was cleared to go ahead and Carty was soon asserting his influence with the first try of the match on 11 minutes.
The 28-year-old creating the try for himself when he intercepted Ross Molony's pass.
Leinster hit back three minutes later with wing Scott Penny sprinting to the try-line after being set up by Luke McGrath, who missed the conversion.
Carty split the posts with a penalty and was on target with a conversion after Wootton went in at the corner on the stroke of half-time.
Leinster improved on the restart and had McGrath dart in near the posts for a converted try and when Baird went over, after good work from Sean Cronin, it left 11 points between the sides.
A third Leinster try, with fly-half David Hawkshaw touching down, was ruled out by the TMO for obstruction on centre Sammy Arnold.
Connacht sealed the bonus point as Daly held off tackles to get in for a try converted by Carty and the victory was already assured when replacement prop Ed Byrne pushed over a try in the final seconds, with Hawkshaw making the conversion.
Leinster v Connacht
Leinster: O'Reilly; Smith, O'Brien, O'Loughlin, Kearney; Sexton, McGrath (capt); Dooley, Tracy, Bent, Molony, Toner, Baird, Penny, Leavy.
Replacements: Cronin, Byrne, Clarkson, Murphy, Conan, O'Sullivan, Turner, Connors.
Connacht: Porch; Sullivan, Arnold, Daly, Wootton; Carty, Blade; Buckley, Delahunt, Robertson-McCoy, Thornbury, Roux (capt), Masterson, Oliver, Masterson.
Replacements: Murphy, Burke, Kenny, Dillane, Prendergast, Marmion, Kilgallen, O'Donnell.
Referee: Chris Busby
