Brumbies centre Christian Lealiifano kicked a controversial penalty after the final hooter to snatch a 23-20 win over the Bulls in Canberra on Saturday.
A gallant fightback in the second half by the Bulls saw the South Africans level the scores 20-20 after trailing 14-3 at half-time and 20-13 after the break with two minutes remaining.
JJ Engelbrecht's 78th-minute try, converted by Morne Steyn, looked to have been enough to secure a draw in the Aussie capital. However, the Brumbies were awarded a penalty in extra time by referee Jonathon White after he pinged Pierre Spies for not releasing the ball in a ruck.
It was the wrong call, as television replays showed Brumbies scrum-half Nic White lying over the ball to indicate that the visitors should have been awarded the penalty instead.
Lealiifano's ensuing three-pointer then broke Bulls hearts, while sending the Canberra crowd into raptures.
The result moves the Brumbies back to the top of the Super Rugby standings after the Chiefs had edged ahead earlier in the round.
Lealiifano, who had only missed one shot at goal in six attempts, booted the Brumbies into a 9-3 lead in the first half. With half-time approaching, the hosts retained possession for more than a dozen phases before full-back Robbie Coleman scrambled over the tryline after the half-time siren.
The Bulls declined a penalty shot directly after half-time, and after several phases winger Lionel Mapoe crashed over the line, only to lose the ball in a late tackle by Brumbies winger Henry Speight.
But winger Jurgen Visser scored in the 49th minute when he finished off a well-worked passage of play from the Bulls.
The Brumbies scrum dominated the Bulls throughout the match, culminating in a yellow card to loosehead prop Morne Mellet in the 65th minute for repeated scrum infringements.
With the Bulls scrum one man down, the Brumbies pressed home their advantage, and nine minutes later Lealiifano kicked his fifth penalty goal of the night after another scrum infringement.
It seemed the Bulls were dead and buried until Engelbrecht struck with his converted try, and the rest - as they say - is history.
Pens: Lealiifano 6
Tries: Visser, Engelbrecht
Cons: Steyn 2
Brumbies: 15 Robbie Coleman, 14 Henry Speight, 13 Tevita Kuridrani, 12 Christian Lealiifano, 11 Joe Tomane, 10 Matt Toomua, 9 Nic White, 8 Ben Mowen (c), 7 George Smith, 6 Peter Kimlin, 5 Etienne Oosthuizen, 4 Scott Fardy, 3 Dan Palmer, 2 Stephen Moore, 1 Ben Alexander.
Replacements: 16 Siliva Siliva, 17 Scott Sio, 18 Fotu Auelua, 19 Colby Faingaa, 20 Ian Prior, 21 Andrew Smith, 22 Clyde Rathbone.
Bulls: 15 Zane Kirchner, 14 Lionel Mapoe, 13 JJ Engelbrecht, 12 Jan Serfontein, 11 Jürgen Visser, 10 Mornè Steyn, 9 Jano Vermaak, 8 Pierre Spies (c), 7 Dewald Potgieter, 6 Deon Stegmann, 5 Juandrè Kruger, 4 Paul Willemse, 3 Werner Kruger, 2 Chiliboy Ralepelle, 1 Morne Mellett.
Replacements: 16 Willie Wepener, 17 Frik Kirsten, 18 Wilhelm Steenkamp, 19 Arno Botha, 20 Ruan Snyman, 21 Louis Fouche, 22 Francois Venter.
Referee: Jonathon White (New Zealand)