A Clayton Daniels own-goal, to go with strikes from Themba Zwane, Mzikayise Mashaba and a brace from Khama Billiat, sent SuperSport spiralling to their worst defeat since a 5-0 loss to Arcadia in 1990.
Sundowns move to 38 points from 20 matches, seven points behind leaders Cape Town City, though they do have a game in hand.
Sundowns made a brilliant start and after Percy Tau had missed two one-on-one chances with SuperSport goalkeeper Reyaad Pieterse, both of which were saved, he finally helped his side break the deadlock.
Billiat picked him out in the box and Tau's low cross came off Matsatsantsa defender Daniels and looped over a stranded Pieterse.
It was almost 2-0 before 15 minutes when Hlompho Kekana saw his header strike the crossbar.
SuperSport could not stem the tide and it was no surprise when Sundowns doubled their advantage on 18 minutes.
Tebogo Langerman's low shot was deflected into the path of Zwane, who had the simple task of shooting into an empty net.
SuperSport were carved open again on 26 minutes when Billiat held off Daniels and fed Mashaba with a backheel, and the winger blasted the ball into the back of the net.
Billiat grabbed a goal for himself a minute before haltime when his low drive from the edge of the area skipped off the wet surface past Pieterse and went in off the post.
Billiat netted his second of the night just past the hour-mark when he side-footed the ball home from 12-yards to compound United's misery.