Walcott scored Arsenal's first and was the inspiration behind their victory
Arsenal produced a dominant attacking display to beat 10-man Villarreal and set up a Champions League semi-final showdown with Manchester United.
Theo Walcott scored an early first goal, collecting a Cesc Fabregas flick before running clear and chipping in.
Emmanuel Adebayor put the hosts firmly in charge, producing a neat finish with the outside of his right foot.
Sebastian Eguren was then sent off for disputing an Arsenal penalty that Robin van Persie scored to seal the victory.
In 2006 Arsenal faced Villarreal in a Champions League semi-final and after securing a 1-0 first-leg advantage would have paid for their defensive approach to the second leg had Jens Lehmann not saved Juan Roman Riquelme's last minute penalty.
Partly due to this chastening experience, and partly because of the loss of a number of key defenders through injury, Arsene Wenger decided attack was the most effective form of defence.
From the off, Arsenal bit into tackles, were the first to loose balls and sought to release the superb Walcott down the right at every opportunity.
Every time the England winger received the ball he threatened to embarrass the Villarreal defence, in particular his marker - the Spanish international full-back Joan Capdevila.
It was a break from Walcott that created the Gunners' first chance.
His initial cross evaded Van Persie in the box but Fabregas was able to collect on the opposite wing and find the Dutch striker with a cross, which he headed over the bar.
Walcott's next contribution to the game was even more significant.
Emmanuel Eboue's forward pass was flicked on by Fabregas into the path of Walcott, who bore down on goal and lured out Villarreal keeper Diego Lopez before exquisitely chipping the ball over him to reward his side's initial endeavour.
For all the talk of Arsenal's defensive fallibility in the absence of William Gallas, Bacary Sagna, Manuel Almunia and Gael Clichy, it was the Spaniards who were vulnerable.
It would be simplistic to blame the absence of influential midfielder Marcos Senna from the Villarreal side when so many of his team-mates' performances were lacking.
In one incident Gonzalo Rodriguez twice plunged his side into trouble.
Wenger credits accumulated confidence
His needless foul on Adebayor on the edge of the box gave Van Persie the chance to strike a free-kick that Lopez could not hold and Adebayor's follow-up header was almost knocked over the line by the defender before he finally cleared.
The start to the second half was not quite as frenetic as the first but this did not prevent Arsenal from seizing their opportunity to take firm control of the tie.
Van Persie picked up the ball in the Villarreal half and drove forward before neatly playing in Adebayor whose finish, with the outside of his right foot, was too good for Lopez.
Arsenal's control of the tie was converted into certain qualification nine minutes later.
Walcott dribbled into the box from the right and drew a rash challenge from Diego Godin, prompting the referee to point to the spot.
The Villarreal players protested vociferously, pointing out that the linesman had not signalled for a penalty.
Referee Wolfgang Stark took exception and brandished a second yellow card to Eguren, resulting in his dismissal.
Unperturbed by the raised emotions of the opposition, Van Persie strode up and fired in the penalty to the left of Lopez.
All three goalscorers were substituted soon after and rightly received a standing ovation.
Two of the replacements - Nicklas Bendtner and Abou Diaby - combined late on to almost score the Gunners' fourth but the latter flashed his shot across goal after being fed by the former.
Fabianski, Eboue, Toure, Silvestre, Gibbs, Walcott (Denilson 77), Song Billong, Fabregas, Nasri, Adebayor (Bendtner 83), Van Persie (Diaby 77).
Subs Not Used: Mannone, Eduardo, Vela, Ramsey.
Walcott 10, Adebayor 60, Van Persie 69 pen.
Diego Lopez, Angel, Rodriguez, Godin, Capdevila, Cani (Pablo 70), Eguren, Bruno (Nihat 64), Fernandez (Ibagaza 64), Pires, Rossi.
Subs Not Used: Viera, Llorente, Javi Venta, Fuentes.
Eguren, Cani, Godin.
Wolfgang Stark (Germany).
BBC Sport Player Rater man of the match:
Arsenal's Theo Walcott 8.65 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished
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