Match ends, Arsenal 0, Tottenham Hotspur 2.
Goals from Son Heung-min and Dele Alli gave Tottenham victory over bitter rivals Arsenal and secured a two-legged Carabao Cup semi-final against Chelsea.
Son pounced on Alli's smart ball over the top to put Spurs in front after just 20 minutes at the Emirates.
Alli then coolly chipped it over keeper Petr Cech with the outside of his boot in the second half to make it 2-0.
The England midfielder was then hit on the head by a plastic bottle thrown from the crowd shortly after that goal.
It was a heated atmosphere at what was the second north London derby in 18 days; victory ensured Spurs made the last four for the first time since 2014-15.
Back then, they went on to the final and were beaten by Chelsea - their semi-final opponents this time around.
Spurs will be at home in the first leg, scheduled for the week commencing 7 January, with the return at Stamford Bridge a fortnight later. Holders Manchester City will take on League One side Burton in the other semi-final.
Tottenham keeper Paulo Gazzaniga made two good saves in the first half of Wednesday's quarter-final - denying Henrikh Mkhitaryan from close range and later tipping Aaron Ramsey's volley on to the post.
In the second half, Alexandre Lacazette hit the post and Pierre-Emerick Aubameyang's cross curled onto the top of the crossbar before Christian Eriksen's fizzing shot was saved by Cech.
Arsenal had not lost back-to-back matches prior to this defeat since they were beaten by Manchester City and Chelsea in the Premier League back in August.
Spurs rotation pays off
Mauricio Pochettino's decision to make four changes and leave Harry Kane out of the starting line-up paid off.
Son, Kane's replacement, caused problems in the first half and made his mark, scoring after just 20 minutes to make Tottenham's possession count.
The South Korean striker has now scored three goals in as many appearances in the League Cup this season.
When Kane was eventually introduced after 57 minutes - for his first appearance in the competition since September 2015 - he made an instant impact, setting up Alli with a perfectly weighted ball over the top.
The ability to rest and rotate will aid Tottenham in a busy festive period, which will see them play four matches in 10 days.
'A step backwards for Arsenal' - analysis
Former Aston Villa striker Dion Dublin on BBC Radio 5 live:
Arsenal might be taking a step backwards based on this performance. It feels like the same old Arsenal - no backbone.
I thought they'd got out of this zone they've been in for a long time where they didn't have the backbone, with the hard-working players putting their head in where it hurts. Of late, they've been outstanding. But this game tonight makes me think: 'Don't take a step backwards.'
Arsenal looked a bit tired, a bit leggy. They created decent chances but weren't clinical. Spurs were men. Big, strong men who stood up to be counted in the derby. Arsenal were slightly spineless.
Spurs deserve to be in the last four.
'A very difficult draw' - what they said
Tottenham manager Mauricio Pochettino: "It is a very difficult draw, another London derby [in the semi-finals against Chelsea]. We have already played Watford, West Ham and Arsenal.
"We shall see. Chelsea are a great team but we are excited. To be in the semi-final is fantastic for us.
"I am very pleased. The most important thing was to play well and win the game [against Arsenal]. We deserved it. We kept a clean sheet here after a very busy period.
Tottenham's Dele Alli on being hit by a plastic bottle: "It is what it is. It made the goal even sweeter, and the win. We knew how important it was - a big test. It was a strong performance in the end."
Son making his mark - the best of the stats
- Arsenal have been eliminated from the League Cup by Spurs for the first time since 2008, the season in which Spurs went on to win the competition (2-1 against Chelsea in the final).
- This was just Spurs' second win against Arsenal at Emirates Stadium in all competitions (D5 L10), and their first since November 2010 (3-2 in the Premier League).
- Arsenal have lost back-to-back games in all competitions for the first time since August, in what were Unai Emery's first two competitive games in charge.
- This was the 14th meeting between Arsenal and Spurs in the League Cup; the joint-most played fixture in competition history (with Arsenal v Liverpool).
- Paulo Gazzaniga is the first Spurs goalkeeper to keep a clean sheet away at Arsenal in any competition since November 1998, when Espen Baardsen did so at Highbury.
- Alli was directly involved in both of Spurs' goals (one goal and one assist), as many as he had been in his previous seven games against Arsenal combined (two).
- Son Heung-min has had a hand in five of Spurs' last nine goals in the League Cup (three goals and two assists).
- 34XhakaBooked at 77mins
- 29GuendouziBooked at 45minsSubstituted forNketiahat 65'minutes
- 7MkhitaryanSubstituted forKoscielnyat 45'minutes
- 17IwobiSubstituted forLacazetteat 58'minutes
- 27Lucas MouraSubstituted forKaneat 58'minutes
- 20AlliBooked at 85mins
- 23EriksenBooked at 90mins
- 7Son Heung-MinSubstituted forLamelaat 79'minutes
- Jonathan Moss
- Shots on Target
Second Half ends, Arsenal 0, Tottenham Hotspur 2.
Attempt missed. Lucas Torreira (Arsenal) right footed shot from outside the box misses to the left. Assisted by Granit Xhaka following a set piece situation.
Christian Eriksen (Tottenham Hotspur) is shown the yellow card.
Nacho Monreal (Arsenal) wins a free kick in the attacking half.
Foul by Moussa Sissoko (Tottenham Hotspur).
Attempt missed. Dele Alli (Tottenham Hotspur) header from the centre of the box is too high. Assisted by Kieran Trippier.
Foul by Laurent Koscielny (Arsenal).
Harry Kane (Tottenham Hotspur) wins a free kick in the attacking half.
Nacho Monreal (Arsenal) wins a free kick in the defensive half.
Foul by Harry Kane (Tottenham Hotspur).
Laurent Koscielny (Arsenal) wins a free kick in the attacking half.
Foul by Harry Kane (Tottenham Hotspur).
Dele Alli (Tottenham Hotspur) is shown the yellow card.
Offside, Tottenham Hotspur. Erik Lamela tries a through ball, but Dele Alli is caught offside.
Corner, Tottenham Hotspur. Conceded by Petr Cech.
Attempt saved. Christian Eriksen (Tottenham Hotspur) right footed shot from outside the box is saved in the top centre of the goal. Assisted by Harry Kane.
Delay over. They are ready to continue.
Delay in match Ainsley Maitland-Niles (Arsenal) because of an injury.
Laurent Koscielny (Arsenal) wins a free kick in the defensive half.