Swansea City 1-0 Manchester City
Manchester City lost their Premier League lead for the first time in five months as their title hopes were dented by superb Swansea City.
Unmarked substitute Luke Moore headed the hosts' winner inside the final seven minutes as he guided in Wayne Routledge's pin-point right-wing cross.
Manchester City, who drop a point behind rivals Manchester United following the Red Devils' win over West Bromwich Albion, did have a late Micah Richards goal ruled out for offside in a dramatic final few minutes.
Swansea could have won more comfortably, visiting keeper Joe Hart saving Scott Sinclair's early penalty.
But the Welsh side will settle for a single-goal victory against the league leaders that will rank alongside their January triumph over Arsenal as one of the most famous results in their 100-year history.
More importantly, it edges Swansea closer to Premier League survival, having reached a tally of 36 points that would have seen them retain their top-flight status in 10 of the last 13 seasons.
But, as much as Swansea celebrate, Roberto Mancini's men will feel frustration at having squandered their top-of-the-table berth with a below-par performance.
The visitors were dominated for the majority of the first half and Routledge had already blasted a close-range shot over Hart's crossbar when the Swansea winger won a penalty after being brought down in the penalty area inside five minutes.
Hart was penalised but immediately made amends, the England keeper diving to his right to save Sinclair's weak spot-kick.
It was the first time Sinclair had missed a penalty in 14 attempts but the England Under-21 winger did not look confident as he slid the ball too close to Hart.
Routledge, replacing the suspended Nathan Dyer, was again proving to be the main tormentor.
He tested Hart's reactions when he flicked Sinclair's corner goalwards from close range, only for the England keeper to gather with consummate ease.
Swansea top scorer Danny Graham then turned to shoot Gylfi Sigurdsson's incisive pass wide as the hosts dominated territory and possession against a Manchester City side feeling the effects of their midweek Europa League defeat in Porto.
Mancini said before the game he wanted his side to break Chelsea's title-winning points record of 95 set in 2005. But they were restricted to half chances against a side that have also taken points off Arsenal, Chelsea and Tottenham Hotspur at the Liberty Stadium this season.
Yaya Toure fumbled as he enjoyed a rare sight of Swansea's goal, David Silva fired harmlessly wide and Mario Balotelli summed up the visitors' frustrations as the enigmatic Italian tried his luck from virtually the halfway line with a wayward effort.
Mancini even went to the lengths of making a first-half tactical substitution, as £35m striker Sergio Aguero was introduced in place of Gareth Barry in an effort to spark the Manchester side into life.
But it was to no avail as Swansea continued to create the better chances and Graham's low driven ball across the six-yard box should have been tapped in by Joe Allen but the Swans midfielder failed to connect and it was cleared by Kolo Toure, captain for the day in Vincent Kompany's absence.
The visitors had a penalty appeal waved away by referee Lee Mason after Balotelli went down under a challenge by Allen but he did not appear to be touched by the Wales midfielder and, in any case, fell outside the box.
But, with virtually his first touch of the game after replacing Graham, Moore claimed victory when he headed in only his second league goal of the season at the far post.
Mancini's men responded but, after having a snapshot well saved by Swans keeper Michel Vorm, Richards had an effort disallowed by assistant referee Sian Massey for offside.
And Swansea kept out the late bombardment to claim not only a famous scalp, but almost certainly their Premier League status too - with 10 games still remaining.