Falkirk earned a stunning first victory over an abject Celtic in 19 years to move up to fourth place in the Scottish Premiership.
Ethan Ross' early goal was added to by Scott Tanser's excellent run and finish before the break as John McGlynn's side ruthlessly exposed Celtic's defensive frailties.
Martin O'Neill's league leaders did come close on a number of occasions, with Camilo Duran denied by a post and Falkirk goalkeeper Scott Bain in stunning form throughout.
Defeat leaves Celtic with a record of three wins from their last 10 outings as they failed to extend their four-point advantage lead at the top of the table.
Falkirk struck with their first attack and Celtic played a huge role in the concession. The returning Cameron Carter-Vickers was so lax, diverting the ball straight to Ross, who slammed in from close range.
A response came but it never came to enough. Duran raced in behind and angled a shot off the far post, before Bain produced a wonderful save to deny Haissem Hassan's curling effort on the rebound.
Bain intervened so many times it got slightly ridiculous. His display was top drawer.
Falkirk's second goal arrived in stunning style. Owen Eames played a superb pass to Tanser, who burst through the defence to slot home beautifully. Celtic's defence was ripped wide open.
Celtic rung the changes and had several glaring chances but couldn't breach the home side as Falkirk earned a famous victory that will live long in the memory.