A first half strike from Tom Rogic gave Neil Lennon’s side a half-time lead, before a three goal burst in four minutes late in the second half finished off the Saints.
Odsonne Edouard struck the second from the penalty spot on 79 minutes before substitute Ryan Christie added a third on 82 with David Turnbull finishing off the scoring a minute later.
St Mirren rarely troubled the Celtic goal as the defending Scottish Premiership champions wrapped up a third consecutive victory.
Here’s how the Celtic players rated in the 4-0 rout ...
Player ratings scale - 10: One of the best performances you've seen. 9: Outstanding. 8: Very good. 7: Good. 6: Average. 5: Poor, 4: Very poor. 3: A terrible day at the office. 2: Abysmal. 1: One of the worst performances you've seen.
1. Scott Bain - 6
A comfortable evening for the goalkeeper who was barely called into action. Photo: Craig Williamson - SNS Group
2. Jonjoe Kenny - 7
Two key moments at either end of the pitch. Helped set up the first goal for Rogic and made a vital interception in the first half to prevent a clear chance for a St Mirren equaliser. Photo: Ross MacDonald - SNS Group
3. Kris Ajer - 7
A composed and commanding performance from the Norwegian. St Mirren couldn't get the ball off him when he strode out of defence. Photo: Craig Foy - SNS Group
4. Stephen Welsh - 6
A mixed bag from the young centre-back. A bit scratchy with his passing at times but rarely caught out of position. Left field on a stretcher after nasty tackle from Jon Obika. Photo: Ross Parker - SNS Group