David Raya made two stunning penalty shootout saves as Arsenal advanced to the quarter-finals of the UEFA Champions League for the first time since 2010 by eliminating Porto.
The Gunners trailed 1-0 from the first leg in Portugal, but Leandro Trossard levelled the tie in the first half with a cool finish.
Report: Arsenal 1-0 Porto (AET, 4-2 pens)
But chances were at a premium in the second half and during a tense extra-time period as the tie went to a penalty shootout.
Martin Odegaard, Kai Havertz, Bukayo Saka and Declan Rice all scored their penalties, while Raya denied Wendell and Galeno as Arsenal won the shootout 4-2.
How the match unfolded
Mikel Arteta made one change from the side that beat Brentford 2-1 last weekend, with Raya returning in goal in place of Aaron Ramsdale, after the on-loan Spaniard was ineligible to face his parent club.
Arsenal applied early pressure on the Portuguese side, with Saka unable to direct his header on target, although Porto were soon able to find a foothold in the contest.
But Arsenal kept probing and levelled the tie after 41 minutes through Trossard, who found the bottom corner with an angled shot following a delightful one-two with Odegaard, for the Norwegian's first assist in the competition.
The second half came to life after 67 minutes when Odegaard put the ball into an empty net, but the goal was disallowed for a shirt pull by Havertz on Pepe in the build-up.
Moments later, Raya kept out a powerful low strike from Francisco Conceicao as the tie remained on a knife edge.
Arteta made an attacking first change, with Gabriel Jesus replacing Jorginho, and the Brazilian was denied seconds after coming on by a brilliant save from Claudio Ramos.
Shortly after, Saka's shot was parried into the path of Odegaard, whose effort went narrowly wide, as neither side could find the decisive goal to end the tie in 90 minutes.
Both teams struggled to create clear-cut opportunities in the first half of extra-time, but Saka went close in the second period, with his shot blocked by Otavio.
But it remained 1-0 as the tie went to penalties, the first shootout in the competition since the 2016 final between Real Madrid and Atletico Madrid.
Raya proved to be the matchwinner as he tipped Wendell's penalty on to a post and clear before keeping out Galeno's spot-kick to book Arsenal's spot in the quarter-finals to the delight of a raucous Emirates Stadium.
It ends a run of seven consecutive last-16 eliminations in the competition for Arsenal.
The Gunners are next in action on Sunday 31 March, when they face a HUGE title showdown at champions Manchester City.
Arsenal fixtures
| Date | Fixture |
|---|---|
| 31 Mar | Man City v Arsenal |
| 3 Apr | Arsenal v Luton |
| 6 Apr | Brighton v Arsenal |
| 9/10 Apr | Champions League quarter-final first leg |
| 13 Apr | Arsenal v Aston Villa* |
| 16/17 Apr | Champions League quarter-final second leg |
| 20 Apr | Wolves v Arsenal** |
*Fixture could move due to European match
**Fixture will be rescheduled if Wolves progress to the FA Cup semi-finals
The draw for the quarter-finals will be made at 11:00 GMT on Friday, with the first legs taking place on 9/10 April, and the second legs scheduled for 16/17 April.