Match ends, Chelsea 0, Bournemouth 1.
Bournemouth manager Eddie Howe said his side went through "a lot of soul searching" before their late win at Chelsea.
Dan Gosling's goal, which was awarded by the video assistant referee (VAR), gave the injury-hit Cherries their first victory since early November in a scrappy encounter at Stamford Bridge.
The result ended their five-match losing streak and handed them their third away win of the season. Their last Premier League points had come on 2 November, when they beat Manchester United at home.
"It's been a really difficult run, a lot of soul searching has gone on," Howe told BBC Match of the Day. "We've lost a lot of players to injuries and we had to step up to a really tough test.
"We had to come up with something slightly different because if you do the same things you get the same result.
"In the second half I thought we were a real threat in the match and we could have scored more. Our goalkeeper at the other end made some big saves."
The match looked to be heading for a goalless draw when Gosling flicked the ball over his and Blues keeper Kepa Arrizabalaga's head, the effort originally ruled out for offside before VAR awarded the goal.
Bournemouth - who move up to 14th in the table - have now beaten Chelsea three times in their five Premier League visits to Stamford Bridge, the latest consigning Chelsea to their fourth league defeat in their last five matches.
Frank Lampard's side lacked tempo and creativity and were undone by a resolute Bournemouth defence, but their manager rejected suggestions it was a reality check for his team.
"Maybe for the fans and the players, but not for me," he told BBC Radio 5 Live. "I didn't get excited in the great run that we had, the Premier League is tough and I felt there was a lot of improvement needed, and that's proved true."
He added: "I think it's a reaction time for everybody, myself, the players. Fans are coming here and watching us at home struggle to beat teams that we should beat.
"I expected us to offer more to break a team down that was as organised as Bournemouth were.
"Sometimes you can work on things all week and recreating them on a match day is a difficult thing. Today we were too slow with the ball."
Cherries rewarded for battling performance
With Howe forced to choose from a depleted squad after Nathan Ake became the latest to join the Cherries' considerable injury list, he made four changes to the side who lost to Liverpool last week, with Gosling - one of four central midfielders selected - making his first start of the season after a hip injury.
The visitors started brightly in the first half, Lewis Cook proving troublesome in an unfamiliar wide midfield role before Ryan Fraser had a shot smothered by Arrizabalaga.
By half-time, they had enjoyed just 34% of the possession but that was not reflective of the challenge they posed to Chelsea, rarely allowing the Blues a chance on goal with Cherries keeper Aaron Ramsdale stopping those they did carve out.
There was a rise in tempo at the start of the second half as Chelsea found a much-needed second gear, with Cook going in the book for a lunging tackle on Emerson.
Bournemouth's ventures into Chelsea's half were few and far between but when they did cross the halfway line, their hosts looked far from comfortable with Joshua King enjoying several forays forward.
Ramsdale denied Emerson from point-blank range as the match headed for a stalemate before substitute Dominic Solanke - replacing King, who rolled off the pitch after picking up a knock - almost got a touch a few feet out from Arrizabalaga's goal.
But Chelsea were left shellshocked after Gosling's goal - one of only two shots on target the Cherries had.
With his back to goal, Gosling perfectly flicked the ball over and in, with the Bournemouth end of Stamford Bridge erupting as VAR made its decision.
Chelsea lack zest in frustrating show
Chelsea came into this match on the back of a 3-1 defeat by Everton last week, a match in which, once again, their vulnerabilities in defence had been on show.
Lampard brought in Antonio Rudiger to face Bournemouth for only his second league appearance this season and the Germany international shone in the Blues' defence, making more clearances and winning more possession than any of his team-mates.
In an uneventful first half, Chelsea's performance was lifeless, Mason Mount having perhaps the best opportunity to put his side ahead only to be denied by a solid Ramsdale save.
Willian showed glimpses of magic at the heart of every attack the Blues managed to put together, but they went into the interval having been unable to break down Bournemouth's defence - and showing no sign of ideas of how they might.
When the second half got under way, they looked to have raised their game as they rained in attack after attack , with Emerson going closest to scoring.
But Mateo Kovacic scuppered a late chance to equalise, and Chelsea have now lost two of their last three league home games - as many as they had in the previous 28.
Man of the match - Dan Gosling (Bournemouth)
- Since they were promoted to the Premier League in 2015, no side has won more top-flight away games against Chelsea than Bournemouth (three, level with Liverpool).
- Chelsea have lost two of their last three Premier League home games (W1), as many as they had in their previous 28 at Stamford Bridge (W16 D10 L2).
- Having scored in 14 consecutive home league games, Chelsea have now failed to score in two of their last three at Stamford Bridge.
- Chelsea have lost five of their 14 home games in all competitions this season, just one fewer than they had in 62 games over 2017-18 and 2018-19 combined.
- Bournemouth had just two shots on target in this match - the first of the game in the third minute before Gosling's 84th-minute winner.
- Gosling scored his first Premier League goal since April, in what was his first start of the season.
Chelsea travel across London to face Tottenham on Sunday, 22 December (16:30 GMT), while Bournemouth host Burnley the day before (15:00 GMT).
- 5JorginhoSubstituted forBatshuayiat 78'minutes
- 10WillianSubstituted forHudson-Odoiat 65'minutes
- 22PulisicSubstituted forKovacicat 65'minutesBooked at 81mins
- 16L CookBooked at 50mins
- 4GoslingBooked at 82mins
- 7KingSubstituted forSolankeat 75'minutes
- Graham Scott
- Shots on Target
Second Half ends, Chelsea 0, Bournemouth 1.
Attempt saved. Mateo Kovacic (Chelsea) right footed shot from outside the box is saved in the bottom left corner.
Corner, Chelsea. Conceded by Diego Rico.
Kepa Arrizabalaga (Chelsea) wins a free kick in the defensive half.
Dangerous play by Philip Billing (Bournemouth).
Foul by Callum Hudson-Odoi (Chelsea).
Diego Rico (Bournemouth) wins a free kick in the defensive half.
Attempt blocked. Dominic Solanke (Bournemouth) right footed shot from the left side of the six yard box is blocked. Assisted by Dan Gosling.
Offside, Chelsea. Antonio Rüdiger tries a through ball, but Tammy Abraham is caught offside.
VAR Decision: Goal Chelsea 0-1 Bournemouth (Dan Gosling).
Goal! Chelsea 0, Bournemouth 1. Dan Gosling (Bournemouth) right footed shot from the centre of the box to the top right corner. Assisted by Jefferson Lerma with a headed pass following a corner.
Attempt blocked. Dan Gosling (Bournemouth) left footed shot from the centre of the box is blocked. Assisted by Diego Rico with a cross.
Corner, Bournemouth. Conceded by Antonio Rüdiger.
Dan Gosling (Bournemouth) is shown the yellow card for a bad foul.
N'Golo Kanté (Chelsea) wins a free kick in the defensive half.
Foul by Dan Gosling (Bournemouth).
Mateo Kovacic (Chelsea) is shown the yellow card for a bad foul.
Foul by Mateo Kovacic (Chelsea).
Dominic Solanke (Bournemouth) wins a free kick in the defensive half.