Manchester City's Barclays Premier League title aspirations were dealt a major blow as Luke Moore's late header saw Swansea once again upset one of the top-flight big guns with a 1-0 win at the Liberty Stadium.
Substitute Moore had only been on the field a matter of minutes when he rose at the far post to head Wayne Routledge's cross beyond Joe Hart.
It could have been worse for City had Scott Sinclair converted an early penalty, although Mario Balotelli and Sergio Aguero spurned good chances for the visitors and Micah Richards had a header ruled out in the dying moments.
Defeat sees Roberto Mancini's side, who have topped the table since October, fall behind rivals Manchester United after their win against West Brom.
For Swansea the win moves them ever closer to survival, with a 14-point gap to the bottom three all but guaranteeing them another season in the Premier League.
Swansea had already beaten Arsenal at their Liberty Stadium home and drawn with Chelsea and Tottenham this season, and their confidence was clear to see during a bright opening.
Swansea stunned the visitors as they snatched the lead with just seven minutes to go.
Yaya Toure was caught in possession and the Welsh side coolly worked Routledge in down the right to deliver a cross that Moore, just on as a substitute for Danny Graham, headed beyond Hart's despairing dive.
Mancini's men thought they had salvaged a point when Richards headed in as Michel Vorm came and failed to reach a cross, but the full-back was correctly ruled offside.
Sinclair almost added a second in added time as Swansea broke after Hart had gone up for a corner, but his strike from halfway came up short of the line as the keeper recovered.