Arsenal got their pursuit of a place in the Premier League's top four back on track as they ended a run of three defeats with a crucial victory at Chelsea.
The Gunners had slipped from looking in pole position to secure a place in next season's Champions League but this win will provide renewed belief.
Eddie Nketiah was given the nod ahead of out-of-sorts Alexandre Lacazette in Arsenal's attack and he rewarded manager Mikel Arteta's faith when he took advantage of Andreas Christensen's header with a composed finish in the 13th minute.
It was the start of a chaotic first half as Timo Werner equalised with a deflected shot four minutes later before Emile Smith Rowe showed a real touch of class to beat Chelsea keeper Edouard Mendy from the edge of the area.
Chelsea were back on terms again before the break through captain Cesar Azpilicueta but Nketiah pounced on a series of defensive errors to put Arsenal back in front after 57 minutes.
Bukayo Saka was outstanding for Arsenal and he got the reward his performance deserved when he sealed the win from the spot in added time after he was hauled down by Azpilicueta.
The Gunners are now level on points with north London rivals Tottenham with a derby at Emirates Stadium still to come.
Arsenal produce at crucial moment
Questions about Arsenal's character and ability to maintain a fight for a top-four finish were starting to be asked after three damaging defeats but this was a display showing plenty of grit.
Arsenal were brave and on the front foot right from the start, pressing Chelsea into mistakes and refusing to buckle even when Thomas Tuchel's side equalised twice.
Nketiah was the headline-grabber with two goals but Saka and Smith Rowe showed Arsenal have two real gems for the future.
Saka gave Marcos Alonso a tough time on Arsenal's right flank, helping to create Smith Rowe's goal, setting up other chances then scoring the fourth with a penalty after he was fouled.
Smith Rowe demonstrated great composure to finish smoothly for his 11th goal of the season, a fine tally for this richly promising 21-year-old playmaker.
Arsenal now face struggling Manchester United at Emirates Stadium on Saturday lunchtime feeling much better about themselves after a deserved triumph.
More to follow.
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Chelsea
Squad number16Player nameMendy
Squad number24Player nameJames
Squad number4Player nameChristensen
Squad number31Player nameSarr
Squad number28Player nameAzpilicueta
Squad number12Player nameLoftus-Cheek
Squad number7Player nameKanté
Squad number3Player nameAlonso
Squad number19Player nameMount
Squad number9Player nameLukaku
Squad number11Player nameWerner
Squad number6Player nameThiago Silva
Squad number22Player nameZiyech
Squad number29Player nameHavertz
Arsenal
Squad number9Player nameLacazetteSquad number17Player nameCédric SoaresSquad number35Player nameGabriel MartinelliLine-ups
Chelsea
Formation 3-4-1-2
16Mendy
24James4Christensen31Sarr
28Azpilicueta12Loftus-Cheek7Kanté3Alonso
19Mount
9Lukaku11Werner
16Mendy24James4ChristensenSubstituted forThiago Silvaat 45'minutes31SarrBooked at 65mins28AzpilicuetaBooked at 90mins12Loftus-Cheek7Kanté3AlonsoSubstituted forZiyechat 81'minutes19MountBooked at 84mins9LukakuSubstituted forHavertzat 60'minutes11WernerSubstitutes
1Arrizabalaga5Jorginho6Thiago Silva10Pulisic14Chalobah17Saúl18Barkley22Ziyech29HavertzArsenal
Formation 4-2-3-1
32Ramsdale
4White16Holding6Gabriel20Tavares
25Elneny34Xhaka
7Saka8Ødegaard10Smith Rowe
30Nketiah
32Ramsdale4White16Holding6GabrielBooked at 90mins20Tavares25Elneny34Xhaka7SakaSubstituted forLacazetteat 90+5'minutes8Ødegaard10Smith RoweSubstituted forCédric Soaresat 75'minutes30NketiahSubstituted forMartinelliat 70'minutesSubstitutes
1Leno9Lacazette17Cédric Soares19Pépé23Sambi Lokonga35Martinelli38Azeez69Swanson82HutchinsonReferee:Jonathan MossAttendance:32,249Live Text
Match ends, Chelsea 2, Arsenal 4.
Second Half ends, Chelsea 2, Arsenal 4.
Substitution, Arsenal. Alexandre Lacazette replaces Bukayo Saka.
Goal! Chelsea 2, Arsenal 4. Bukayo Saka (Arsenal) converts the penalty with a left footed shot to the bottom right corner.
César Azpilicueta (Chelsea) is shown the yellow card.
Gabriel Magalhães (Arsenal) is shown the yellow card.
Penalty conceded by César Azpilicueta (Chelsea) after a foul in the penalty area.
Penalty Arsenal. Bukayo Saka draws a foul in the penalty area.
Corner, Chelsea. Conceded by Rob Holding.
Attempt missed. Nuno Tavares (Arsenal) right footed shot from more than 35 yards is high and wide to the left.
Mason Mount (Chelsea) is shown the yellow card for a bad foul.
Foul by Mason Mount (Chelsea).
Cédric Soares (Arsenal) wins a free kick in the attacking half.
Attempt missed. Nuno Tavares (Arsenal) right footed shot from the left side of the box misses to the left. Assisted by Cédric Soares.
Foul by Malang Sarr (Chelsea).
Martin Ødegaard (Arsenal) wins a free kick in the defensive half.
Substitution, Chelsea. Hakim Ziyech replaces Marcos Alonso.
Attempt missed. Bukayo Saka (Arsenal) right footed shot from the centre of the box misses to the left. Assisted by Cédric Soares.
Substitution, Arsenal. Cédric Soares replaces Emile Smith Rowe.
Substitution, Arsenal. Gabriel Martinelli replaces Eddie Nketiah.
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