Tom Bradshaw's clinical double piled the misery on Aston Villa as Barnsley claimed a deserved 3-1 win.
The Tykes clinched just their second victory over Villa in their history as they extended the hosts' winless run to nine games.
Adam Armstrong's penalty put the visitors ahead before Bradshaw struck either side of Jonathan Kodjia's effort just before the break.
Barnsley's only previous triumph over Villa came in 1998, but they merited this victory which kept them within six points of the Sky Bet Championship play-off places.
Defeat left Villa seven points above the relegation zone, despite spending over £60million this season which was supposed to bring them an instant return to the Premier League.
Aston Villa 1-3 Barnsley
