Huddersfield Town ended Manchester United's unbeaten start to the season as Jose Mourinho's side fell five points behind league leaders Manchester City at the John Smith's Stadium.
United had only conceded twice in eight league games this season, but they doubled that tally in five first-half minutes following two sloppy mistakes that were punished by the home team.
Juan Mata gave the ball away to Aaron Mooy in midfield and after he fed Tom Ince, whose shot was saved by David De Gea, the Australian was first to the rebound to sweep home from 10 yards as the United defence watched on.
Then Swedish defender Victor Lindelof - on as a substitute for the injured Phil Jones and making just his second Premier League appearance - misjudged a goal kick by Jonas Lossl and Laurent Depoitre raced onto the loose ball and rounded De Gea to double the Terriers' lead on 33 minutes.
Mourinho made a double substitution at half-time, bringing on Marcus Rashford and Henrikh Mkhitaryan, and the former gave United hope with 12 minutes remaining, nodding in a terrific cross by the otherwise quiet Romelu Lukaku.
But despite a nervy finale and with United enjoying almost 80% of possession, the Terriers clung on to record their first league win against United since 1952 and end a run of six league games without a win.