Ollie Watkins struck Villa’s winner in the 77th minute off a free kick by Douglas Luiz shortly after Saints had been controversially denied the opening goal by VAR.
Browsing: James Ward-prowse
A first win in 10 matches stopped Saints’ alarming slide and moved them 10 points clear of the bottom three.
Southampton had looked in control after Jan Bednarek headed in James Ward-Prowse’s corner in the 23rd minute before Ward-Prowse beat De Gea 10 minutes later with a curling free kick.
Goals from James Ward-Prowse and Che Adams ensured Carlo Ancelotti’s side became the final club to lose a game this season.
Southampton’s win over fellow strugglers Fulham on Wednesday put the spring back in their step but manager Ralph Hasenhuttl says his team’s fight for Premier League survival is far from over.