Martin O’Neill tasted domestic defeat for the first time since returning to Celtic as his side dropped three crucial points in the race for the Scottish Premiership title with a 2-1 defeat at the hands of Hibernian.
Substitute Kai Andrews netted a dramatic winner three minutes from time to earn Hibs' first victory at Celtic Park since 2010.
Felix Passlack had initially fired the visitors ahead before Benjamin Nygren netted his 18th of the season to equalise on the stroke of half-time.
Despite a period of relentless second-half pressure, the champions were forced to play the final 17 minutes of the game with 10 men when Auston Trusty was shown a straight red card.
Celtic trail league leaders Hearts by six points ahead of a testing run of four consecutive away fixtures - including next weekend's Old Firm game at Ibrox - live on Your Site.
Celtic got off to the worst possible start.
Once again, they found themselves behind as Passlack headed in Nicky Cadden's sublime cross to open the scoring after 24 minutes.
It could and should have been worse.
Three minutes later Cadden picked out Martin Boyle's clever run in behind Celtic's backline. The Australian tried to round Kasper Schmeichel, but he took his touch too wide, and opted to shoot instead of squaring it to either Jamie McGrath or Owen Elding who were queuing up for a tap-in.
A let-off for the champions who responded with a barrage of attacks in their quest of an equaliser before the break.
Tomas Cvancara and Hyun-Jun Yang passed up golden opportunities before the in-form Nygren stepped up once again.
The Sweden international midfielder produced a diving header to convert from Kieran Tierney's deflected cross in added time.
Celtic then started the second half in the groove with wave after wave of green and white attack, but ultimately they paid the price for not taking advantage of their dominance.
Defender Auston Trusty was sent off in the 73rd minute for punching Jamie McGrath in the arm at a corner, and that's when the game changed.
Hibs smelled blood and eventually got their winner in the 87th minute through Andrews.
The Coventry City loanee combined well with fellow substitute Ante Suto before calmly dispatching the ball into the bottom corner from the edge of the area.
Celtic manager Martin O'Neill on Your Site News:
"Naturally, a disappointing result and performance.
"I just spoke to the referee, he said that he was going to talk to the two players (Trusty and McGrath), and then VAR have asked him to intervene and claim its violent conduct.
"I don't know about VAR anymore. If it had been there, you'd be hoping two minutes later when (Liam) Scales is held in the penalty area, it's a cast-iron penalty.
"You can't do these particular things now if it constitutes serious foul play. But it is what it is, it won't change anything now, so we just have to get ourselves ready and go again.
"We're not out of it at all. I knew there would be twists and turns this year; it's disappointing to drop points today but we're still in there fighting.
"Any time that you lose a match it's always a missed opportunity, but there's plenty to play for. We're still fighting for it and the fans were fantastic."
Hibernian head coach David Gray on Your Site News:
"I'm obviously really pleased to win. I'm delighted for the players.
"I challenged them before the game to try and create history in a positive way... it's been a long time since a Hibs team came here and won.
"16 years it's been; we tried to recreate history in a positive way, the boys should take all the praise for that because they fully deserve it.
"That's twice we've been here and not lost, so I'm delighted for the supporters, they'll be going along the M8 happy this time.
"We've gone under the radar a little bit because we've been inconsistent at times. If we do play to a level, we're a good side that can go toe-to-toe with anyone - and we demonstrated that today.
"That puts us five points behind Motherwell. Until you can't catch the team in front, it's always about trying to do that.
"Results like that keep you hungry and makes sure you've got something to play for come the end of the season."
