Alexandre Lacazette netted twice and Pierre-Emerick Aubameyang scored late on as Arsenal overturned an early deficit to lead 3-1 after the first leg of their Europa League semi-final with Valencia on Thursday evening.
Los Che took the lead 11 minutes in at the Emirates Stadium through Mouctar Diakhaby's close-range header and wasted a couple of good chances to extend their lead.
Arsenal soon recovered, though, and they were in front thanks to two Lacazette goals in the space of seven first-half minutes.
The tie remained finely poised heading into the final minute of the first leg, but Aubameyang converted at the back post to ensure that the North London outfit have a big advantage ahead of next week's return match at the Mestalla.
Arsenal's run to this stage of the competition has been built on their solid form at the Emirates Stadium, but they conceded for the first time in 461 minutes at home in Europe when Diakhaby popped up with an early goal.
Two minutes after Ezequiel Garay had somehow fired Rodrigo Moreno's pass over the bar from a couple of yards out, Arsenal's defensive deficiencies were again clear to see as Diakhaby outjumped three opponents to head home another Rodrigo knockdown.
The home side were all over the place in the first 15 minutes of the match, coming close to conceding another goal when Daniel Parejo's shot was parried by Petr Cech, before Goncalo Guedes looped the ball over the bar after Ainsley Maitland-Niles nodded it right into his path.
Arsenal soon clicked into gear and scored through their first attempt of the match, with Lacazette sliding the ball through for Aubameyang and then converting into an empty net once his strike partner returned it to him inside the area.
Lacazette then nodded Granit Xhaka's cross into the ground and past Neto, who was positioned behind the line when slapping it away, to put the Gunners in front and move himself level with Ian Wright for the most European semi-final goals for the club.
The home team took control of the match in the lead-up to half time, creating another good opportunity that Aubameyang failed to take as his volley from Xhaka's latest dangerous cross bounced over the crossbar.
Valencia seemed happy to sit back and take a one-goal deficit into the return fixture, and it took Arsenal until 20 minutes into the second half before they created their next opportunity.
Aubameyang crossed the ball for Lacazette to attack on the edge of the six-yard box, only for the French striker to get his body shape all wrong and completely miss the ball.
Lacazette wasted an even better chance three minutes later, this time failing to beat Neto at his near post once teed up by Aubameyang.
Those misses nearly proved costly as Diakhaby got to a corner ahead of Cech and was denied only by Shkodran Mustafi on the line, while Kevin Gameiro was kept out by Cech through his first meaningful touch of the ball after being brought off the bench.
The potentially decisive fourth goal of the tie fell Arsenal's way, though, courtesy of Aubameyang's finish from a tight angle.
Neto produced a superb save to deny Lacazette a hat-trick, but Sead Kolasinac sent the loose ball into the six-yard box and Aubameyang was there to convert, leaving Valencia requiring a couple of goals next week.
ARSENAL (3-4-1-2): Cech; Mustafi, Koscielny (Monreal 82'), Sokratis; Maitland-Niles, Guendouzi (Torreira 58'), Xhaka, Kolasinac; Ozil (Mkhitaryan 75'); Aubameyang, Lacazette
VALENCIA (5-4-1): Neto; Roncaglia, Gabriel, Garay, Diakhaby, Gaya; Piccini, Soler (Wass 71'), Parejo, Guedes (Gameiro 71'); Moreno (Mina 88')