Chiefs pipped in Sydney
The Waratahs have survived a second-half fight-back from defending champions the Chiefs to record a crucial 25-20 upset victory and keep their Super Rugby finals hopes alive at Allianz Stadium.
But momentum turned when the hosts were reduced to 14 men after Sitaleki Timani was yellow carded for a high shot on Tim Nanai-Williams just after the interval.
The Chiefs took advantage of the extra man when Aaron Cruden stepped through and sent Gareth Anscombe flying over under the posts for a converted try.
Brendan McKibbin answered immediately with a penalty goal but the visitors had all the momentum and closed within five points on the hour via two Anscombe penalty goals.
The visitors peppered the Waratahs' tryline and were twice held up before tighthead prop Ben Tameifuna barged over to give the Chiefs their first lead of the contest in the 72nd minute.
But the hosts held their nerve, with Bernard Foley delivered a perfect short ball for reserve hooker John Ulugia to score under the posts and seal a vital victory in front of 15,451 fans.
Foley had a hand in all three of the Waratahs' tries, while man-of-the-match Folau saved two tries and was dangerous with every touch in another strong performance.
A hamstring injury to winger Drew Mitchell soured the win slightly and Chiefs full-back Andrew Horrell suffered a suspected broken ankle.
The win lifts the Waratahs to seventh on the Super Rugby ladder, two points out of the top six, while the Chiefs remain in second spot for now despite their second straight loss.
The Waratahs made a promising start and hit the front with a McKibbin penalty goal in the third minute.
They suffered a setback when Mitchell limped from the field but his replacement Peter Betham almost scored with his first touch after Bernard Foley put Michael Hooper into space with a brilliant flick pass.
The hosts didn't have to wait too long for their opening try, debutant Cam Crawford crossing in the 15th minute.
Adam Ashley-Cooper charged onto a short pass from Bernard Foley and beat Aaron Cruden before linking with an unmarked Crawford on his outside to make it 8-0.
Anscombe and McKibbin both hit the woodwork with penalty attempts before Folau ignited the crowd with a spectacular try two minutes from the break off a Foley cross-kick.
The former rugby league international and AFL recruit soared into the stratosphere to outleap Lelia Masaga and Anscombe and score his fourth try of the season to send the hosts into the sheds with a handy half-time buffer.
Anscombe had a chance to post points before the break but pushed his penalty attempt wide as the Chiefs failed to trouble the scorers in the first half for the first time this season.
Waratahs 25 (Crawford, Folau, Ulugia tries; McKibbin 2 cons, 2 pens)
Chiefs 20 (Anscombe, Tameifuna tries; Anscombe 2 cons, 2 pens)