Match ends, Arsenal 1, Chelsea 2.
Chelsea overcame an "awful" start, said boss Frank Lampard, as they staged a stunning late comeback to snatch victory and wreck Mikel Arteta's return to Emirates Stadium as Arsenal manager.
Arteta, taking charge of his first home game since succeeding the sacked Unai Emery, looked on course for three important points after Pierre-Emerick Aubameyang's early header put the Gunners in front.
Chelsea, with Lampard making a first-half tactical switch when he introduced Jorginho for the struggling Emerson, were gifted an equaliser seven minutes from time when goalkeeper Bernd Leno hopelessly misjudged Mason Mount's free-kick to leave the substitute with a simple finish.
Arsenal were doubly frustrated because Jorginho was fortunate to escape a second yellow card earlier for a cynical foul on Lucas Torreira - but Arteta's home bow was to get even more painful.
Chelsea struck again with three minutes of normal time left, Tammy Abraham turning Arsenal substitute Shkodran Mustafi far too easily in the area to beat Leno and complete the smash-and-grab raid.
"We were so awful for the first 30 minutes; slow, lethargic, nervous," Lampard told BBC Sport.
"We gave Arsenal everything they wanted. We made the change early, felt it had to be done, and second half we dominated.
"You can accept a miss-pass but you can't accept lethargy in a London derby. The players were told that and they delivered. The second half was nothing to do with tactics, it was all to do with spirit and desire."
Arsenal, who lost defender Calum Chambers to injury in the first half, will start 2020 11 points behind fourth-placed Chelsea and without a Premier League home win since 6 October.
It is the first time they have lost four consecutive home matches in all competitions since December 1959.
- Plenty of promise despite defeat for Arteta - Keown analysis
- 'Arteta's Arsenal homecoming transformed into wake'
- Reaction from Emirates Stadium and Sunday's Premier League games
Arteta learning the hard way
Arteta understandably looked downcast as he and his players took sympathetic applause from their fans after they were left stunned by Chelsea's late surge.
For the first half-hour Arsenal dominated a desperately poor Chelsea and there was much to encourage everyone inside a vibrant Emirates Stadium as the new era kicked into life.
The Gunners, however, ran out of steam towards the end of the first half as Chelsea, helped by Lampard removing Emerson and sending on Jorginho, started to dominate and continued to do so after the break.
Arsenal were resilient but were hanging on and ultimately it was a calamitous individual error and familiar defensive fragility that was to prove their undoing.
Leno's rush of blood left Jorginho with the easiest of finishes, although Arsenal certainly had a case to complain about his continued presence on the pitch after escaping that second yellow card.
And then Mustafi, on for the injured Chambers, was at fault when he allowed Abraham far too much time to control, turn and score the winner.
Arteta will have seen some good signs but ultimately old faults let Arsenal down. There is going to be no quick fix.
Lampard finds a way as Chelsea win
Chelsea boss Lampard clearly felt he got his team selection wrong, as he ditched his three-man central defence and introduced Jorginho after 34 minutes - and deserves great credit for seeing it was not working and putting it right.
It did improve Chelsea but in reality they could not get any worse in a feisty London derby which saw nine players booked.
They took complete control of possession and territory after the break, with Lampard's subsequent substitutions also having an impact.
Teenager Tariq Lamptey was a lively presence down Chelsea's right flank on his Premier League debut after replacing Fikayo Tomori while Callum Hudson-Odoi did well when he came on for Matteo Kovacic.
Lampard looked like he was going to be frustrated by Chelsea's lack of end product once more but they were given that late lifeline by Leno's dreadful error as well as the generosity of referee Craig Pawson in allowing Jorginho to stay on.
Abraham completed the comeback for a dramatic win.
There is a rollercoaster nature to this Chelsea side, as proved by their results, a home defeat by Southampton sandwiched in between wins at Tottenham and Arsenal, but they got the job done to cement their place in the Premier League's top four.
Man of the match - Jorginho (Chelsea)
'It was very cruel' - Arteta reaction
Arsenal head coach Mikel Arteta: "It was very cruel the way we lost it, in the first half we saw a lot of positives and saw what we are trying to implement. But the way we conceded was disappointing.
"It was clear why it was disappointing, I don't need to say any more.
"Our reaction was right, we were doing the right things, it is hard to dominate all periods of the game against this team. We started to defend too deep and our energy levels are in a different place to Chelsea's.
"We need to sustain those periods for longer periods in the game and against top sides. Individual errors cost you games but I can't fault the effort, commitment and for putting in place what we practised."
Leno's costly errors - the stats
- Chelsea are the first team to win five away Premier League games against Arsenal at Emirates Stadium.
- Since his Premier League debut in February 2018, Arsenal's Pierre-Emerick Aubameyang has scored 45 league goals - 22 more than any other Gunners player in that time.
- Arsenal goalkeeper Bernd Leno has made more errors leading to goals than any other Premier League player since August 2018 (seven).
- Only Manchester City's Raheem Sterling and Leicester City's Jamie Vardy (nine each) have scored more away Premier League goals than Chelsea striker Tammy Abraham (eight) this season.
- Chelsea became the first team to come from behind at half-time to win away at Arsenal in the league since Tottenham in November 2010.
- There were nine yellow cards in this match, the most in a Premier League game this season and most since February, when there were nine in Bournemouth's game against Wolves.
- After taking the lead in the 13th minute, Arsenal had just three shots, and none on target.
Arsenal have another heavyweight home game on New Year's Day when Manchester United visit Emirates Stadium (20:00 GMT) while Chelsea are away at Brighton on the same day (12:30 GMT).
- 15Maitland-NilesBooked at 90mins
- 21ChambersSubstituted forMustafiat 23'minutes
- 23David LuizBooked at 47mins
- 11TorreiraBooked at 73mins
- 29GuendouziBooked at 10mins
- 24NelsonSubstituted forPépéat 86'minutes
- 10ÖzilSubstituted forWillockat 76'minutes
- 9LacazetteBooked at 77mins
- 32Smith Rowe
- 2RüdigerBooked at 34mins
- 29TomoriSubstituted forLampteyat 59'minutes
- 7KantéBooked at 30mins
- 17KovacicSubstituted forHudson-Odoiat 70'minutes
- 33EmersonSubstituted forJorginhoat 34'minutesBooked at 55mins
- 19MountBooked at 30mins
- Craig Pawson
- Shots on Target
Second Half ends, Arsenal 1, Chelsea 2.
Foul by César Azpilicueta (Chelsea).
Nicolas Pépé (Arsenal) wins a free kick in the defensive half.
Attempt missed. Lucas Torreira (Arsenal) left footed shot from the centre of the box misses to the left. Assisted by Joseph Willock with a cross.
Attempt missed. Tammy Abraham (Chelsea) right footed shot from the right side of the box is too high.
Foul by Callum Hudson-Odoi (Chelsea).
Lucas Torreira (Arsenal) wins a free kick in the defensive half.
Ainsley Maitland-Niles (Arsenal) is shown the yellow card for a bad foul.
Callum Hudson-Odoi (Chelsea) wins a free kick on the left wing.
Foul by Ainsley Maitland-Niles (Arsenal).
Goal! Arsenal 1, Chelsea 2. Tammy Abraham (Chelsea) right footed shot from the centre of the box to the centre of the goal. Assisted by Willian following a fast break.
Tammy Abraham (Chelsea) wins a free kick in the defensive half.
Foul by Shkodran Mustafi (Arsenal).
Substitution, Arsenal. Nicolas Pépé replaces Reiss Nelson.
VAR Decision: Goal Chelsea - Arsenal 1-1 Chelsea (Jorginho).
Goal! Arsenal 1, Chelsea 1. Jorginho (Chelsea) right footed shot from very close range to the bottom right corner. Assisted by Mason Mount with a cross following a set piece situation.Goal confirmed following VAR Review.
Jorginho (Chelsea) wins a free kick on the left wing.
Foul by Alexandre Lacazette (Arsenal).
Attempt blocked. Callum Hudson-Odoi (Chelsea) right footed shot from outside the box is blocked. Assisted by Willian.