Kilmarnock ended Celtic's unbeaten run in the league with a last gasp Matt Kennedy winner at Rugby Park.
The result means Brendan Rodgers' side still stay top of the Scottish Premier League, with the gap to rivals Rangers currently sitting at five points, but Kilmarnock move to fifth.
Matt O'Riley opened the scoring after Calum McGregor showed some excellent footwork to force a save out of Will Dennis in the Kilmarnock net.
O'Riley was there to pounce on the lose ball and knotch his ninth league goal of the season so far.