A magnificent strike from St Johnstone midfielder Danny Swanson inflicted a first domestic defeat of 2015 on Celtic and gave Aberdeen a fresh glimmer of hope that the title race is still alive.
The on-loan Coventry midfielder marked his first Scottish Premiership start for Saints with a glorious first-time effort in the 54th minute to hand the visitors a 1-0 victory.
Swanson showed brilliant technique to fire the ball into the top corner from 25 yards after Virgil van Dijk had headed David Wotherspoon’s corner out of the box.
The goal sent St Johnstone into the top six and gave Aberdeen fresh hope in the title race following their 4-0 defeat at Parkhead on Sunday.
Celtic never hit the heights that had earned them 10 domestic victories in a row this year and Saints goalkeeper Alan Mannus was well worthy of his clean sheet after making some important saves.
Celtic had the chance to move nine points clear but they remain two victories ahead of the Dons with both teams having now played 27 matches.