Alex Iwobi scored the winning penalty for Arsenal as they defeated Chelsea 6-5 on penalties after a 1-1 draw in front of a crowd of 46,000 people at the Aviva Stadium.
The Gunners came back with an injury-time goal to equalise and force penalties, and then won the game in the shoot-out.
Earlier the boos had rang out around Lansdowne Road in the opening minutes for former Arsenal player Cesc Fabregas as he came across to take the corner but the Spaniard silenced his detractors, sending a fantastic corner onto the head of Antonio Rudiger who powered home a free header to give Chelsea the lead.
Chelsea youngster Callum Hodson–Odoi was the best player on the pitch in the opening 45 minutes, with his lightening pace causing havoc for the Arsenal rear guard.
Alvaro Morata had a number of chances to put Chelsea further ahead. A magnificent Fabregas pass left him through on goal but he sent his effort wide.
Minutes later a superb outstretched glove from Petr Cech denied the Spanish striker another glorious chance to get himself on the scoresheet.
Arsenal eventually settled into the game as the first half wore on, with some mesmerising passing between Arsenal’s front three of Ozil, Smith-Rowe, and Aubameyang.
The trio of forwards were finding each other effortlessly with their passing and probing the Chelsea defence.
Chances came for Smith- Rowe and Aubameyang but neither troubled Willy Caballero in the Chelsea goal.
Arsenal were the brighter team in the opening stages of the second half but like the first, it was Chelsea who had the first real opportunity ten minutes in.
The pace of Hudson–Odoi again causing major problems on the left for Arsenal.
The young Chelsea midfielder showed great vision to look up and square the ball for Morata but Cech was quick to confront him and force the shot wide.
Both sides began to empty their bench on the hour mark with Alex Iwobi being introduced for Arsenal and Abraham, Ampadu, Moses, and Zappacosta taking to the field for Chelsea.
It was a much quieter second half in terms of chances from both sides with Arsenal having the edge ever so slightly.
Minutes later, a beautiful through ball from Mesut Ozil found Lacazette through on goal with only Caballero to beat.
He tried to place the ball into the far corner but saw his shot drift agonisingly wide of the post.
Iwobi was next to go close for Arsenal who got himself on the end of a deep Calum Chambers cross to the back post but the shot was saved and tipped over by Marcin Bulka.
Although they let Arsenal in a number of times in the second half, Chelsea looked to have seen off the threat until the dying moments, deep into the third minute of stoppage time.
Chelsea thought they had the game won but after some nice interplay, Reiss Nelson fired across goal where striker Lacazette was on his own at the back post to tap the ball into an empty net.
The game went straight to a penalty shootout to decide the winner.
It took four penalties each before Ruben Loftus-Cheek missed for Chelsea, with Cech saving well.
It was up to Iwobi to win it for Arsenal who made no mistake and powered home a great penalty to give Arsenal the win.
Petr Cech, Hector Bellerin (Calum Chambers 82), Sokratis Papastathopoulos, Shikodran Mustafi, Mohamed Elneny, Henrikh Mkhitaryan (Reiss Nelson 73), Mesut Ozil, Matteo Guendouzi, Sead Kolasinac (Ainsley Maitland – Niles 70),Emile Smith Rowe (Alex Iwobi 62), Pierre–Emerick Aubameyang (Alexandre Lacazette 73)
Willy Caballero (Marcin Bulka 75), Antonio Rudiger ( Ethan Ampadu 63), David Luiz (Danny Drinkwater 46), Marcos Alonso (Emerson 63), Cesar Azpilicueta (Davide Zappacosta 63), Cesc Fabregas (Andreas Christensen 46), Jorginho (Ruben Loftus-Cheek 75), Ross Barkley, Callum Hudson – Odoi ( Lucas Piazon 86), Pedro ( Victor Moses 63), Alvaro Morata (Tammy Abraham 63),