Hibs failed in a bid to win their opening six league games for the first time in their history as Ayr United fought back from a goal down to take all three points at Easter Road.
The game turned on a sending off for Hibs midfielder Marvin Bartley halfway through the second period. The hosts were 1-0 up at the time through a tremendous Jason Cummings strike and were looking well in control of the contest.
Former Hearts defender Conrad Balatoni headed the visitors back into the match, converting a Brian Gilmour corner at the front post. Gilmour then completed the turnaround by side-footing home a Nicky Devlin cross.
The defeat knocks Hibs from the top of the Ladbrokes Championship table, halting their 100 per cent and grants Ayr United their second successive victory, which moves the part-time side up into sixth.
It looked like it was going to be a particularly straight-forward afternoon's work for the hosts when Grant Holt almost had them in front in the second minute. The big striker got his head to David Gray's cross but couldn't direct it beyond Greg Fleming in the Ayr goal.
Holt turned provider in the tenth minute, crossing for Andrew Shinnie. The on loan Birmingham midfielder couldn't make clean contact with his effort, which bounced into the arms of Fleming.
Holt hit the post soon after - though the linesman's flag on the far corner, ignored by the ref at the time, indicated the effort would not have stood - before Lewis Stevenson saw his first time shot from a tight angle held by the Ayr stopper.
Despite Hibs controlling possession, most of it in Ayr's half, the underdogs did well to limit the amount of clear-cut opportunities the hosts would have throughout the afternoon. The next chance came via a free-kick, as Fraser Fyvie rippled the side netting from 20 yards as time ticked down towards the half.
Rejuvenated after the break, Hibs got off to a flyer at the beginning of the second period when Cummings curled in a terrific effort from 25 yards that looped over Fleming and into the top corner.
From there a Hibs victory seemed inevitable and the only question would be by how many goals. Shinnie and Cummings each had two chances apiece to extend the advantage, and the wastefulness in front of goal would come back to haunt them after Bartley's ordering off. The midfielder was shown a straight red card for a lunge on Jamie Adams 10 yards into the Ayr United half.
Ayr had earlier gone close with a header from a corner on the left side, which had to be cleared off the line by Fraser Fyvie, and it was a warning Hibs would not heed as Ayr equalised with almost an exact replica of that chance. This time Balatoni squeezed it past goalkeeper Ofir Marciano and the defender on the line.
Ayr, with their confidence soaring, went in search of a winner and found it when Devlin's cut-back found Gilmour all alone in the penalty area. The midfielder had the simple task of passing the ball beyond Marciano from six yards out.
Hibs pressed for an equaliser, but when substitute Martin Boyle could only divert an injury time cross wide of the post, any chance of rescuing something from the game was lost.