Match ends, Swansea City 1, Chelsea 0.
Swansea City claimed an impressive first Premier League win against Chelsea to all but secure their top-flight survival.
The Swans seized on a tepid Chelsea display to dominate the first half and lead through Gylfi Sigurdsson's volley.
The visitors enjoyed more possession after the break but were stifled by the hosts, who are now 13 points clear of the relegation zone.
Chelsea stay 10th after a first league defeat under manager Guus Hiddink.
The reigning champions had been unbeaten in 14 Premier League games under the Dutchman, though they surrendered that record meekly at the Liberty Stadium.
Swansea, by contrast, produced what was arguably the most accomplished performance of head coach Francesco Guidolin's tenure.
Return of revitalised Montero
Starting the match 10 points above the bottom three and with survival all but guaranteed, the Swans selected a more attacking team with Jefferson Montero the orchestrator of a vibrant team display.
With injury and a loss of form curbing his progress after a sparkling start to the season, the Ecuadorian winger was making his first start under Guidolin.
Montero probed menacingly at Chelsea's defence and created the game's first chance for Sigurdsson, whose firm shot was palmed away by Asmir Begovic.
It was the same formula which produced the opening goal, as Montero's cross was only half-cleared into the path of Sigurdsson, who guided a left-footed volley into the bottom corner.
Montero ran relentlessly on Swansea's left flank, as Chelsea defenders Cesar Azpilicueta and Matt Miazga were both booked for fouls on the 26-year-old.
Conte shadow hangs over sloppy Chelsea
Miazga was substituted at half-time, and Chelsea were fortunate not to be further behind at the break as Sigurdsson and Andre Ayew both had shots saved by Begovic.
It was a ragged display from the visitors, who were playing their first game since confirming Italy manager Antonio Conte would take over at Stamford Bridge after Euro 2016.
The former Juventus boss is likely to have been unimpressed by Chelsea's sloppy defending in south Wales, while their efforts in attack left much to be desired.
Brazilian forward Alexandre Pato was underwhelming on his first start, looking short of match fitness and squandering two promising chances.
Chelsea began to control possession as the match wore on, with Swansea dropping deep as they sensed a precious win was within their grasp.
Despite keeping the ball for long periods, however, Chelsea seldom troubled Lukasz Fabianski in the home goal.
Man of the match - Jefferson Montero
What they said
Swansea manager Francesco Guidolin: "This is the first victory in the Premier League for Swansea against Chelsea and I am happy and proud. We played very well in the first half, we deserved to score other goals.
"It's a very important win for our fans. It's a good afternoon for our players, our club and our fans. Jefferson Montero is an important player for us. Safety is almost real, but I hope to take other points in the next weeks because it's important to finish well."
Chelsea manager Guus Hiddink: "Every defeat hurts but everyone knows the situation we are in, so there's a positive side to bringing in youngsters and seeing what they can do. We defended poorly and gave Sigurdsson a very free chance. We were attacking, attacking, but in the final third we were not sharp enough."
The stats you need to know
- Combined with his first spell at Chelsea, it was only Guus Hiddink's second loss in the Premier League (W17 D9).
- Only Harry Kane (11) and Sergio Aguero (10) have scored more Premier League goals in 2016 than Gylfi Sigurdsson.
- Swansea's past six home league games have produced just seven goals, with no side scoring more than once in any of those fixtures.
- The Swans have won three consecutive Premier League home games for the first time since March 2013.
- Chelsea have failed to win away from home when Asmir Begovic has played in the Premier League this season (D2 L5).
Chelsea host Manchester City on April 16 as they bid to hang on to their top-half status, while Swansea visit relegation-threatened Newcastle on the same day.
- 22RangelBooked at 30mins
- 6WilliamsBooked at 77mins
- 3TaylorBooked at 43mins
- 8FerBooked at 79mins
- 10A AyewSubstituted forRoutledgeat 67'minutes
- 23G Sigurdsson
- 20MonteroSubstituted forNaughtonat 84'minutes
- 9PaloschiBooked at 70minsSubstituted forGomisat 75'minutes
- 4Ki Sung-yueng
- 28AzpilicuetaBooked at 36mins
- 20MiazgaBooked at 40minsSubstituted forKenedyat 45'minutes
- 4FàbregasBooked at 77mins
- 36Loftus-CheekSubstituted forFalcaoat 76'minutes
- 17PedroBooked at 71mins
- 11Da SilvaSubstituted forTraoreat 64'minutes
- Andre Marriner
- Shots on Target
Second Half ends, Swansea City 1, Chelsea 0.
Attempt blocked. Kyle Naughton (Swansea City) right footed shot from the centre of the box is blocked. Assisted by Bafétimbi Gomis.
Branislav Ivanovic (Chelsea) wins a free kick in the defensive half.
Foul by Bafétimbi Gomis (Swansea City).
Corner, Chelsea. Conceded by Kyle Naughton.
Attempt saved. Falcao (Chelsea) left footed shot from the centre of the box is saved in the top left corner. Assisted by Bertrand Traore with a through ball.
Substitution, Swansea City. Kyle Naughton replaces Jefferson Montero.
Foul by César Azpilicueta (Chelsea).
Leroy Fer (Swansea City) wins a free kick in the defensive half.
Corner, Chelsea. Conceded by Angel Rangel.
Leroy Fer (Swansea City) is shown the yellow card for a bad foul.
Oscar (Chelsea) wins a free kick on the left wing.
Foul by Leroy Fer (Swansea City).
Cesc Fàbregas (Chelsea) is shown the yellow card.
Ashley Williams (Swansea City) is shown the yellow card.
Substitution, Chelsea. Falcao replaces Ruben Loftus-Cheek.
Attempt missed. Jefferson Montero (Swansea City) header from the centre of the box is just a bit too high. Assisted by Gylfi Sigurdsson with a cross.
Substitution, Swansea City. Bafétimbi Gomis replaces Alberto Paloschi.
Ruben Loftus-Cheek (Chelsea) wins a free kick in the attacking half.