Jordan Petaia rounded off a remarkable comeback from the Reds with a last-gasp try as they dealt the Brumbies their first defeat in Super Rugby AU this season in a 40-38 thriller.
The defending champion Brumbies led 24-16 at half-time of a rematch of last year's final and stretched their advantage to 15 points after Folau Fainga'a went over for his second try.
But Taniela Tupou and Harry Wilson crossed within six minutes of each other to trim the gap to a point and James O'Connor's penalty kept the Reds within striking distance even after Issak Fines' try had briefly settled Brumbies' nerves.
Yet it was Petaia who had a stunning final say, displaying superb handling to gather Hunter Paisami's low kick and touch down.
O'Connor slotted over a simple yet crucial conversion to clinch victory for the impressive Reds, who have three wins from three and are just two points behind leaders the Brumbies, who have played a game more.
In the Super Rugby Aotearoa tournament, the Crusaders breezed to a 39-17 win over the Chiefs, making it three straight wins to start their title defence.
They led by a slender 11-10 margin at half-time, the first half lit up by an extraordinary finish in the left-hand corner from Leicester Fainga'anuku.
But they ran in four tries after the break and are nine points clear of the Highlanders at the top, albeit having played a game more.