A match-winning try from Glasgow replacement flanker James Eddie sealed a stunning 13-12 victory over Ulster at Ravenhill.
Ulster dominated throughout on a dry evening at redeveloped Ravenhill but they were unable to make their superiority count in the face of a resolute Glasgow defence.
Eventually the home side were made to pay for their profligacy in attack when Eddie hit a great line and surged over the line for the only try of the night to bring Glasgow to within a point at 11-12 with only a matter of seconds left on the clock.
British and Irish Lion Stuart Hogg, who had earlier struck two first-half penalties on his return to club duty, made no mistake with a simple conversion to hand Glasgow the unlikeliest of victories.
Ulster led 12-6 at the break after fly-half Paddy Jackson successfully landed all four of his kicks at goal.
Following the re-start Glasgow spent nearly half an hour in their own 22, but dropped passes from left wing Mike Allen and centre Luke Marshall, under the shadow of the posts, let them off the hook.
David McIlwaine, a late replacement on the right wing for the injured Andrew Trimble, was then held up over the line as Glasgow refused to buckle.
The Scots found themselves reduced to 14 men on 69 minutes when Moray Low received a yellow card, but they finally managed to work their way downfield to fashion the dramatic last-minute score.
Pens: Jackson 4
Pens: Hogg 2
Yellow Card: Low
Ulster: 15 Jared Payne, 14 David McIlwaine, 13 Darren Cave, 12 Luke Marshall, 11 Michael Allen, 10 Paddy Jackson, 9 Ian Porter, 8 Nick Williams, 7 Sean Doyle, 6 Roger Wilson, 5 Dan Tuohy, 4 Johann Muller (capt), 3 Declan Fitzpatrick, 2 Rob Herring, 1 Callum Black.
Replacements: 16 Niall Annett, 17 Tom Court, 18 Ricky Lutton, 19 Iain Henderson, 20 Chris Henry, 21 Paul Marshall, 22 James McKinney, 23 Ricky Andrew.
Glasgow Warriors: 15 Stuart Hogg, 14 Tommy Seymour, 13 Sean Lamont, 12 Mark Bennett, 11 DTH van der Merwe, 10 Ruaridh Jackson, 9 Henry Pyrgos (c), 8 Josh Strauss, 7 Tyrone Holmes, 6 Rob Harley, 5 Jonny Gray, 4 Tim Swinson, 3 Ed Kalman, 2 Pat MacArthur, 1 Ryan Grant.
Replacements: 16 Dougie Hall, 17 Gordon Reid, 18. Moray Low, 19 James Eddie, 20 Chris Fusaro, 21 Richie Vernon, 22 Chris Cusiter, 23 Gabriel Ascarate.
Referee: Ian Davies (Wales)
Assistant referees: Gary Conway, Kevin Beggs (both Ireland)
TMO: Peter Ferguson (Ireland)