James Vaughan struck an 86th-minute winner as Huddersfield claimed a 2-1 win to exact revenge on their West Yorkshire rivals and deal Leeds' npower Championship play-off hopes a major blow.
Vaughan kept his composure to steer home the winner from inside the penalty area after Leeds substitute Aidy White had cancelled out Neil Danns' opener for the visitors early in the second half.
It was a welcome victory for Huddersfield, beaten 4-2 by Leeds at the John Smith's Stadium in December, and lifted them eight points clear of the relegation zone.
Leeds' outside play-off chances appear to be fading fast as they slipped to their first home defeat since early February. They still trail sixth-placed Nottingham Forest by four points, having played a game more than all their rivals.
Jermaine Easter scored with his first touch and Shane Lowry hit a screamer as FA Cup semi-finalists Millwall beat Charlton 2-0.