A double from Cypriot Stelios Demetriou was enough to see the basement boys dump the leaders as the rejuvenated Buddies made it four wins on the trot.
Saints started the match with real intent, the urgency of the home side in stark contrast to that of Hibs who were lacking in ideas and unable to create as they struggled to find their feet on a chilly Paisley evening.
The hosts were the first to threaten in the ninth minute when Cammy Smith turned Marvin Bartley but his weak shot was easily gathered by visiting keeper Ofir Marciano.
St Mirren were on the attack again soon after when Stephen Mallan’s curling effort was just wide of the target.
The Buddies should have gone ahead following their next attack when Mallan picked out John Sutton who headed down to Kyle Magennis but the midfielder’s shot was too close to Marciano who made the save.
Magennis was denied again in the 23rd minute when his volley, from a Lewis Morgan cross, rattled off the crossbar.
Hibs’ first real foray into the Saints half created little other than a dangerous cross from John McGinn which was well beaten away by Billy O’Brien as emergency loan signing Efe Ambrose looked poised to pounce.
Neil Lennon’s men went closer when Andrew Shinnie unleashed a shot from 25 yards, the effort flying narrowly wide on the half hour mark.
It proved a false dawn for the visitors as the Buddies were rewarded for their earlier dominance with ten minutes remaining in the first half when a defence-splitting pass from Mallan found Demetriou who cut inside into the box and lashed the ball into the net.
Hibs might have been level two minutes before the break when Fraser Fyvie found space inside the Saints box but his shot was wild and spiralled over the bar.
Instead the league leaders found themselves two adrift within a minute of the restart when Demetriou struck again, this time with a speculative effort from fully 35 yards that found its way into the bottom corner of the net.
The hosts pushed for a third and came close on two occasions on the hour when first Stephen McGinn had a shot turned round the post by Marciano before Morgan watched his powerful strike fly just over the bar.
Hibs had a golden opportunity in the 64th minute when John McGinn found Jason Cummings in the box who headed down to Martin Boyle, but his shot from six yards was well saved by O’Brien. Hibs sub Grant Holt latched onto the rebound but his shot was poor, allowing O’Brien to pull off a remarkable double save.
With 73 minutes on the clock the Saints nearly went three in front, a blocked Mallan free-kick causing chaos in the Hibs box before Harry Davis’ shot was well saved by Marciano.
Five minutes later and the hosts squandered another chance. Great interplay from the Saints attack led to Morgan having a clean strike at goal from the edge of the box but the in-form winger slid the ball wide of the post.
Hibs had one final chance in the last minute of play when Brian Graham found Holt but his shot was just past the post.
By this point in the match, you would be forgiven for questioning which team sat where in the league as the hosts continued to dominate play to run out comfortable victors and in doing so closing the gap at the bottom of the table between them and Ayr to five points.