Match ends, Arsenal 3, Valencia 1.
Alexandre Lacazette scored twice as Arsenal came from behind at Emirates Stadium to win the first leg of their Europa League semi-final against Valencia.
Mouctar Diakhaby's header put Valencia in front before Lacazette slotted in Pierre-Emerick Aubameyang's pass.
The Frenchman nodded in Granit Xhaka's cross seven minutes later to make it 2-1 before half-time.
And Aubameyang's late volley ensured Arsenal take a two-goal lead to Spain.
Lacazette should have scored a hat-trick - he fluffed a header from six yards out in the second half and was later denied by goalkeeper Neto on two occasions.
But Arsenal will travel to Valencia for the second leg next Thursday, hoping to avoid a second successive semi-final defeat after they were knocked out by eventual winners Atletico Madrid last year.
- Arsenal's European hopes 50-50 - Emery
- Football Daily: Arsenal and Chelsea close in on Baku final
- Reaction to Thursday's semi-final first legs
Late goal calms the nerves
Arsenal started sloppily in London and Ezequiel Garay's miss from a few yards out was an early warning.
They looked rattled, and things looked bleak for the Gunners when Rodrigo was allowed to head the ball back across goal to set up Diakhaby for the opener.
A loose header from Ainsley Maitland-Niles was almost pounced upon by Goncalo Guedes immediately afterwards but Lacazette's swift equaliser - which came against the run of play - helped settle the nerves.
He started the move himself, providing the through ball for Aubameyang before the Gabonese striker cut it back into the middle and Lacazette fired into an empty net.
The Frenchman was clinical again eight minutes later - powerfully nodding in Xhaka's curling cross at the back post - before Aubameyang's volley bounced off the turf and over the bar.
Valencia still caused Arsenal problems though. Rodrigo and Guedes were pests in attack and Petr Cech was called into action to deny Kevin Gameiro from close range in the second half.
Arsenal were wasteful, too - Lacazette missing two glorious chances before Aubameyang eventually made it 3-1 with a well-timed volley at the back post.
Gunners chasing Champions League spot
Arsenal's hopes of securing Champions League football next season have been lifted by this victory.
Three successive defeats have left Arsenal fifth in the Premier League - one place below Champions League qualification and two points below Chelsea with two games remaining.
Arsenal can of course reach the Champions League by winning this competition, but Chelsea could stand in their way again if they make it to final in Baku.
Manager Unai Emery has vast experience in the Europa League, having won it three years in a row with Sevilla in 2014, 2015 and 2016, and he will relish an opportunity to win silverware in his first season in England.
Victory in Spain will also see Arsenal through to their first European final since 2006.
'If we can go to Baku it will be special'
Arsenal striker Alexandre Lacazette: "We know it's going to be hard [in Valencia] so of course, getting as many goals as we could is better for us.
"I had two more chances where I could have done better but thankfully Aubameyang scored the third one. If we can go to Baku [for the Europa League final] it will be special."
Arsenal manager Unai Emery on BT Sport: "In the first leg we wanted to get a good result, knowing that it would be difficult. We took our moments and the goals in the first half gave us confidence.
"We wanted to win and not to concede a second goal, but we also had to play. The third goal came at the end and for us it was important, but [the tie] continues to be 50-50."
Forward Pierre-Emerick Aubameyang: "I hope that third goal will be important. We started a bit nervous because we lost the last three games, I think that's normal. We are human, but after that we had a good reaction.
"It's our target to reach the final and win this trophy. We will give everything to qualify for the Champions League."
Enjoying home advantage - best of the stats
- Arsenal have progressed from 37 of their 40 ties in all European competition when winning the first leg, although Valencia were one of the three teams to eliminate them, in the 2000-01 Champions League quarter-final.
- This is the 28th time Valencia have lost the first leg of a two-legged European tie - they've ended up winning the tie on 11 previous occasions, most recently against Basel in the 2013-14 Europa League.
- Diakhaby's opener for Valencia was the first home goal Arsenal had conceded in the Europa League since the group stages, ending a run of 460 minutes without conceding.
- Lacazette became only the third player to score twice in a European semi-final match for Arsenal, after Charlie George in the 1969-70 Fairs Cup and Steve Bould in the 1994-95 Cup Winners' Cup.
- Aubameyang has been directly involved in 30 goals in his 28 starts at the Emirates in all competitions (23 goals, 7 assists).
- 27 of Lacazette's 35 goals in all competitions for Arsenal have come at the Emirates Stadium (77%).
Arsenal host Brighton in the Premier League on Sunday, 5 May before travelling to Spain for the second leg of their Europa League tie with Valencia on Thursday.
Valencia travel to Huesca in La Liga on Sunday.
- 6KoscielnySubstituted forMonrealat 82'minutes
- 29GuendouziSubstituted forTorreiraat 58'minutes
- 10ÖzilSubstituted forMkhitaryanat 75'minutes
- 13Murara Neto
- 8SolerSubstituted forWassat 71'minutes
- 12DiakhabyBooked at 31mins
- 10ParejoBooked at 70mins
- 19RodrigoSubstituted forMina Lorenzoat 88'minutes
- 7Gonçalo GuedesSubstituted forGameiroat 71'minutes
- 15Latorre Grueso
- 22Mina Lorenzo
- Clément Turpin
- Shots on Target
Second Half ends, Arsenal 3, Valencia 1.
Corner, Arsenal. Conceded by José Gayá.
Foul by Alexandre Lacazette (Arsenal).
Daniel Parejo (Valencia) wins a free kick in the defensive half.
Goal! Arsenal 3, Valencia 1. Pierre-Emerick Aubameyang (Arsenal) right footed shot from the right side of the six yard box to the bottom right corner. Assisted by Sead Kolasinac with a cross.
Attempt saved. Alexandre Lacazette (Arsenal) right footed shot from outside the box is saved in the top left corner.
Attempt blocked. Henrikh Mkhitaryan (Arsenal) right footed shot from outside the box is blocked. Assisted by Sead Kolasinac.
Substitution, Valencia. Santi Mina replaces Rodrigo Moreno.
Attempt missed. Granit Xhaka (Arsenal) left footed shot from outside the box is high and wide to the left. Assisted by Ainsley Maitland-Niles.
Substitution, Arsenal. Nacho Monreal replaces Laurent Koscielny.
Attempt missed. Kevin Gameiro (Valencia) right footed shot from the right side of the box is too high. Assisted by Daniel Wass following a set piece situation.
Foul by Sead Kolasinac (Arsenal).
Cristiano Piccini (Valencia) wins a free kick on the right wing.
Delay over. They are ready to continue.
Delay in match Gabriel (Valencia) because of an injury.
Foul by Henrikh Mkhitaryan (Arsenal).
Gabriel (Valencia) wins a free kick in the defensive half.
Corner, Arsenal. Conceded by Gabriel.
Lucas Torreira (Arsenal) wins a free kick in the defensive half.