Reece Hodge scored a first-half double as the Rebels ended the Brumbies' 100 per cent Super Rugby Aotearoa record with a resounding 30-12 victory on Friday.
The Brumbies remain top of the ladder, but their hopes of completing a perfect season were dashed at a wet Leichhardt Oval.
Hodge opening the scoring with an early try out wide and he went over again after Brad Wilkin crossed for David Wessels' rampant side.
Joe Powell had put the leaders on the board with a try before Hodge's second of the night, but the Rebels had a commanding 27-7 half-time advantage following Jordan Uelese's try a couple of minutes before the break.
Matt Toomua took his tally to 10 points with a penalty as the Rebels moved just four points behind their opponents in second place, with Will Miller's late try merely a consolation.
Props Scott Sio and Tom Ross sustained injuries on a painful evening for the Brumbies.