Southampton picked up their first league victory over Manchester United at Old Trafford in 27 years to move up to third in the Premier League.
Louis van Gaal’s side failed to record a single shot on target as their 10-match unbeaten league run was ended.
Dusan Tadic scored the only goal of the game when he tapped in calmly from 12 yards after Graziano Pelle’s effort had come back off the near post.
The Reds improved after the goal but Juan Mata missed two good chances.
It is the first time United have been beaten at home since their opening day reverse against Swansea and reaffirms Southampton’s top-four credentials, as Ronald Koeman’s side backed up their home win against Arsenal with another three points.
The visitors had not won at Old Trafford in the top tier since January 1988 – a run stretching back 19 games – and this result was built on a 10th clean sheet in 21 games.
Even after centre-half Toby Alderweireld left the pitch injured in the first half, Southampton remained well-drilled and limited United’s array of attacking talent to very few chances.
United’s front four, plus wing-backs Luke Shaw and Antonio Valencia, cost the club almost £200m in transfer fees but the best they managed in a poor first half was Angel Di Maria’s shot which was dragged past an upright.
Nathaniel Clyne also shot wide for the visitors, while some smart defending from Jose Fonte blocked Robin van Persie’s effort.
The game was being played at a sedate pace and only burst into life when Tadic completed a fine move after good work from James Ward-Prowse and Pelle.
United took off former Southampton full-back Luke Shaw and switched Daley Blind to the left, and the Dutchman’s dangerous deliveries presented the Reds with two good chances to level.
First, he whipped in a dangerous ball which goalkeeper Fraser Forster failed to deal with and Mata’s shot went just wide.
Minutes later, Blind drove a low ball into the box and Mata stabbed over from six yards out.
However Saints held on for arguably their most impressive victory of the season and one which puts them three points clear in the Champions League places.