Eddie Nketiah was the hero for Arsenal as they re-ignited their bid for a top-four finish thanks to a thrilling 4-2 victory at Chelsea.
The Gunners took the lead not once, but twice at Stamford Bridge through goals from Nketiah and Emile Smith Rowe, but on both occasions, Chelsea found a response as Timo Werner's deflected strike and Cesar Azpilicueta's low finish sent the sides in level at the interval.
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The scoring wasn't over in the second half as the Gunners took the lead once again, and it was Nketiah who grabbed his side's third before Bukayo Saka sealed Arsenal's victory from the spot after being hauled down late on by Azpilicueta.
Victory ends a run of three straight defeats in the Premier League for Arsenal and sees Mikel Arteta's side move level on points with fourth-placed Tottenham - who they still have to play towards the end of the season - ahead of another crucial match against Manchester United at the Emirates Stadium on Saturday.
Meanwhile, Chelsea, who suffered a second straight home league defeat, remain third, five points ahead of fifth-placed Arsenal.
What the result means for the Premier League table?
How Arsenal stunned Chelsea at Stamford Bridge...
In what was a frantic first half, Arsenal took the lead when a long hopeful ball over was not dealt with by Andreas Christensen, and his under-hit back pass was picked up by Nketiah, who finished expertly past Edouard Mendy for his first league goal of the season.
Much to the frustration of Arsenal boss Mikel Arteta, the lead did not last long as Chelsea were back on level terms just four minutes later. The Gunners wasted numerous chances to clear the ball before Werner's strike deflected off Granit Xhaka to bring the scores level.
It was proving to be a difficult evening for both defences as Arsenal re-established their lead midway through the opening 45 minutes. Smith Rowe produced another fine finish to round off an excellent team goal, sweeping home into the bottom corner after excellent work from Xhaka and Martin Odegaard in the build-up.
The goals kept coming and the celebrations in the away end were cut short again as Chelsea hit back… again. Cesar Azpilicueta pounced like a striker to get on the end of Mason Mount's ball into the box to take the two sides into the break on level terms.
Chelsea responded to their defensive frailties in the first half by bringing on Thiago Silva for Christensen, but it would be Arsenal who hit the front for a third time.
More indecision in the Chelsea defence allowed the striker to nip in and he poked home after Nuno Tavares' cross had not been dealt with by the Blues' backline.
Another frustrating night for Romelu Lukaku came to an end as Chelsea threw on Kai Havertz as they looked for a third equaliser of the night, but it never came.
Arsenal won a late penalty as Bukayo Saka was dragged to the ground by Azpilicueta, the forward dusting himself off to convert the resulting spot-kick to wrap up a crucial three points for the Gunners.
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Redknapp: 'I like what I saw from Arsenal'
Sky Sports' Jamie Redknapp:
"I do like what I saw from Arsenal. They've shown a bit of character.
"Saka, Nketiah, Smith Rowe they have that devilment in the way they play.
"It's a big result, it makes it wide open again. I think if they'd lost today, it would have been too much for Arsenal to come back from four losses on the spin. They're right back in this race."
Nketiah delivers at just the right time
Analysis from Sky Sports' Oliver Yew:
All the talk before the game was Arsenal's goal-shy strikers.
The Gunners' 1-0 loss to Southampton on Saturday made it 15 games since one of their strikers scored a goal from open play in the Premier League, which was a run which went all the way back to December.
Step forward Eddie Nketiah.
Leading the line for the Gunners at Stamford Bridge, there would have been doubts about Nketiah's inclusion after his performance at Southampton. There were calls for Gabriel Martinelli through the middle and even shouts for Nicolas Pepe to play as a striker.
However, Arteta stuck with the former England U21 striker, and it was a decision that paid dividends as Nketiah produced an excellent performance, grabbing two opportunist goals to lead his side to a crucial victory in the race for the top-four.
The question now is, can he do it again?
"He could be a 4/10 next week, if he wasn't he'd be in the team every week, that's his second start all season," Paul Merson told Sky Sports. "The consistency levels are not there but if he gets it for three or four games then Arsenal come fourth. He's a natural goalscorer.
"He's a natural goalscorer plus he's willing to run beyond. Lacazette wouldn't have chased that first [goal]. He wouldn't have scored those two goals. Even though he's a better footballer, he's not a better finisher."
After a performance like that it's hard to not see him getting an opportunity to back up that performance against Manchester United. "Nketiah is going to be playing against Man Utd at the weekend," former Gunners striker Alan Smith said just after the striker was substituted. "No question of that. That was just what he needed and just what his team and club needed."
What Arsenal need is for him to do it again, and again, and who knows his future, which has been in doubt for a long time, might just still be at Arsenal.
What the managers said...
Chelsea boss Thomas Tuchel: "It was a totally wild and open game in the first half, already at 2-2 after we came back twice. We had a good start but again gave the first goal away, which is impossible to do these things in consecutive matches. But we're doing it. We came back twice and we scored another two in the second half, unfortunately for the wrong side.
"It's a level of mistakes, the number of mistakes in consecutive games here at home, it's impossible at this kind of level. You don't see this. It's simply impossible, but we're doing this at the moment and you cannot win football games like this. It's not about individual players. A defensive performance is a team performance and an offensive performance is a team performance.
"You need to have the tactics right, which is doubtful I had this right, and you need the team selection right, again it's doubtful I had this right. Then it's a game for the players. They get full praise when they do it, when they did it for the last three matches. And they have to face the reality that it's impossible to win matches if you make this amount of mistakes of this calibre. It's simply impossible. I don't see it in any other matches but I see it now in consecutive matches of our games and it has to stop."
Arsenal boss Mikel Arteta: "I said to the players, if you want to be playing Champions League football, you have to go these stadiums and beat the top teams. So they have done it and I'm really proud of them, but I'm more proud of how we've reacted as a group in the past weeks. That gives me more energy to be here.
"What I love is the spirit of these players. When you lose matches, you get punished, you get criticised but for these players I don't care because it's so worth it. They are phenomenal people and as a group they are really growing. To win a London derby away from home and how we did it, I am really happy."
Arsenal's remaining fixtures...
April 23 - Man Utd (h)
May 1 - West Ham (a), live on Sky Sports
May 8 - Leeds (h), live on Sky Sports
May 12 - Tottenham (a), live on Sky Sports
May 16 - Newcastle (a), live on Sky Sports
May 22 - Everton (h)
Chelsea's remaining fixtures...
April 24 - West Ham (h) Premier League,live on Sky Sports
April 28 - Man United (a) Premier League, live on Sky Sports
May 1 - Everton (a) Premier League,live on Sky Sports
May 7 - Wolves (h) Premier League
May 11 - Leeds (a) Premier League, live on Sky Sports
May 14 - Liverpool (Wembley) FA Cup final
May 19 - Leicester (h) Premier League
May 22 - Watford (h) Premier League
What's next?
Chelsea are back at home and back on Sky Sports on Super Sunday when they host West Ham in the Premier League; kick-off 2pm. Arsenal will be back in action on Saturday afternoon when they welcome Manchester United to the Emirates; kick-off 12.30pm.