BBC Sport Walcott scored the winner to send Arsenal into the group-stage draw Arsenal cast aside their recent troubles to reach the Champions League group stage with victory at Udinese in their qualifying play-off second leg.
The Gunners won the first leg 1-0 but Udinese went ahead in Italy through Antonio di Natale's superb header.
Robin Van Persie equalised from Gervinho's pass before Thomas Vermaelen handled a Di Natale corner in the box.
Wojciech Szczesny saved the penalty and Theo Walcott sealed a 2-1 win (3-1 on aggregate) with a fine run and finish.
It capped a critical win for Arsene Wenger's side and means they will be in Thursday's draw for the group stages as they prepare for a 14th consecutive season in the competition proper.
Their preparations were disrupted by Samir Nasri's move to Manchester City and news that Jack Wilshere was facing an extended spell on the sidelines.
Huge pressure had also built on the team and manager Arsene Wenger following their winless - and goalless - start to the Premier League season.
But Arsenal at least carried a one-goal advantage to north-east Italy and, despite the sweltering conditions at Stadio Friuli, they got off to an enterprising start.
Gervinho was released down the left and saw a low cross gathered by Samir Handanovic with Van Persie waiting to pounce, and moments later Walcott stung the goalkeeper's palms from about 20 yards.
Udinese were struggling to keep pace with their opponents' slick passing and movement but, as is often the case, Arsenal failed to make their superiority count and that encouraged the Italians to grow in confidence.
Di Natale crossed for Pablo Armero to bounce a header against the post, Di Natale was then denied by the same piece of woodwork with a low strike from a Mauricio Isla centre.
Handanovic produced a superb double save from Walcott and Van Persie, but at the other end Di Natale almost latched on to a deflected effort from a tight angle - and he made no mistake a few minutes later as the 33-year-old found himself completely unmarked to meet Giampiero Pinzi's dinked cross and steer his header past Szczesny.
Wenger opted for experience over youth at half-time - replacing Emmanuel Frimpong with Tomas Rosicky - and shortly after Alex Song failed to connect with a free header from a Van Persie set-piece, Arsenal were back on level terms.
Gervinho again surged in from the left, this time weaving past Medhi Benatia, and cut the ball back for Van Persie to shoot home from eight yards.
The Dutchman's strike appeared to deflate Udinese and their fans but they were gifted a route back into the tie when Vermaelen handled Di Natale's corner.
Unfortunately for the former Italy international, Szczesny dived to his right and pushed the spot-kick to safety with an outstanding one-handed effort.
That proved to be a pivotal moment, and it was not long before Walcott exchanged passes with Bacary Sagna, sprinted clear and slotted past Handanovic.
Di Natale drilled wide and watched on as a free-kick rebounded off the post, while Van Persie and substitute Armand Traore went close to extending Arsenal's lead.
The Gunners held firm and were left to breathe a huge sigh of relief.
Wednesday, 24 August 2011
Champions Lge qualifyingFinal Result 90:00+2:03 Armand Traore takes a shot. Save by Samir Handanovic. 90:00+1:52 Robin van Persie takes a shot. Save made by Samir Handanovic. Full Time 90:00+1:02 The referee signals the end of the game. 90:00+0:07 Piccoli Neuton takes the direct free kick. 90:00+0:07 Substitution Andrey Arshavin is brought on as a substitute for Theo Walcott. 90:00+0:07 Robin van Persie challenges Pablo Armero unfairly and gives away a free kick. 88:44 Free kick awarded for a foul by Tomas Rosicky on German Denis. German Denis takes the free kick. 86:51 Booking Diego Fabbrini is given a yellow card. 84:46 Free kick taken by Robin van Persie. 84:46 Substitution Giovanni Pasquale replaces Mehdi Benatia. 84:46 Substitution Armand Traore on for Yao Gervinho. 84:46 Foul by Pablo Armero on Aaron Ramsey, free kick awarded. 82:08 Antonio Di Natale produces a shot on goal direct from the free kick, save by Wojciech Szczesny. 82:08 Substitution German Denis on for Mauricio Isla. 82:08 Free kick awarded for a foul by Alex Song on Diego Fabbrini. 81:41 Theo Walcott takes a shot. Save made by Samir Handanovic. 80:32 Free kick awarded for an unfair challenge on Alex Song by Emmanuel Agyemang-Badu. Carl Jenkinson restarts play with the free kick. 78:58 The assistant referee signals for offside against Antonio Di Natale. Wojciech Szczesny restarts play with the free kick. 78:33 Aaron Ramsey takes a shot. Save made by Samir Handanovic. 77:51 Effort from inside the area by Antonio Di Natale misses to the left of the target. 76:37 Theo Walcott is flagged offside by the assistant referee. Indirect free kick taken by Joel Ekstrand. 74:40 Free kick awarded for an unfair challenge on Diego Fabbrini by Tomas Rosicky. 74:34 Piccoli Neuton takes the direct free kick. 74:34 Booking Booking for Carl Jenkinson. 73:37 Bacary Sagna restarts play with the free kick. 73:37 Booking Mehdi Benatia is given a yellow card. 73:36 Booking Theo Walcott booked for unsporting behaviour. 73:15 Theo Walcott fouled by Mehdi Benatia, the ref awards a free kick. 69:21 Booking Bacary Sagna is shown a yellow card. 68:50 Assist on the goal came from Bacary Sagna. 68:50 GOAL - Theo Walcott:Udinese 1 - 2 Arsenal Theo Walcott grabs a goal from inside the penalty box to the bottom left corner of the goal. Udinese 1 (1)-(3) 2 Arsenal. 67:32 Yao Gervinho takes a shot. Save by Samir Handanovic. 67:00 Foul by Emmanuel Agyemang-Badu on Bacary Sagna, free kick awarded. Direct free kick taken by Bacary Sagna. 65:47 Unfair challenge on Aaron Ramsey by Emmanuel Agyemang-Badu results in a free kick. Aaron Ramsey takes the free kick. 63:10 Corner taken by Theo Walcott from the left by-line, clearance by Larangera Danilo. 62:30 Substitution Giampiero Pinzi leaves the field to be replaced by Diego Fabbrini. 60:18 Foul by Giampiero Pinzi on Alex Song, free kick awarded. Free kick taken by Alex Song. 59:23 Outswinging corner taken by Antonio Di Natale, Larangera Danilo takes a shot. Save made by Wojciech Szczesny. 58:41 Power penalty taken by Antonio Di Natale saved by Wojciech Szczesny. Udinese 1 (1)-(2) 1 Arsenal. 58:05 Thomas Vermaelen is penalised for handball and concedes a . 57:56 Booking The referee cautions Thomas Vermaelen for unsporting behaviour. 56:54 Inswinging corner taken by Antonio Di Natale from the right by-line, Tomas Rosicky makes a clearance. 56:06 Emmanuel Agyemang-Badu takes a long range shot harmlessly clearing the crossbar. 54:20 The assist for the goal came from Yao Gervinho. 54:20 GOAL - Robin van Persie:Udinese 1 - 1 Arsenal Goal scored by Robin van Persie from close range low into the middle of the goal. Udinese 1 (1)-(2) 1 Arsenal. 54:10 Tomas Rosicky takes a shot. Emmanuel Agyemang-Badu gets a block in. 52:49 Theo Walcott takes a shot. Save by Samir Handanovic. 51:30 Booking Booking for Mauricio Isla. 49:56 Carl Jenkinson fouled by Pablo Armero, the ref awards a free kick. Robin van Persie delivers the ball from the free kick left-footed from right wing, Larangera Danilo fouled by Johan Djourou, the ref awards a free kick. Samir Handanovic takes the free kick. 47:59 Alex Song concedes a free kick for a foul on Giampiero Pinzi. Mauricio Isla restarts play with the free kick. 45:01 The referee starts the second half. 45:01 Substitution Tomas Rosicky comes on in place of Emmanuel Frimpong. Half Time 45:00+1:14 The ref blows to signal half-time. 45:00+1:03 Free kick awarded for an unfair challenge on Giampiero Pinzi by Yao Gervinho. Giampiero Pinzi takes the direct free kick. 44:29 Corner taken by Robin van Persie, Headed effort from deep inside the penalty area by Alex Song misses to the left of the goal. 42:58 Shot from just outside the box by Pablo Armero goes over the target. 38:33 Assist on the goal came from Giampiero Pinzi. 38:33 GOAL - Antonio Di Natale:Udinese 1 - 0 Arsenal Antonio Di Natale finds the net with a headed goal from inside the area. Udinese 1 (1)-(1) 0 Arsenal. 35:32 Corner taken right-footed by Antonio Di Natale, Thomas Vermaelen makes a clearance. 32:41 Antonio Di Natale takes a shot. Wojciech Szczesny makes a save. 32:25 Giampiero Pinzi takes a shot. Blocked by Thomas Vermaelen. 32:01 Robin van Persie takes a shot. Larangera Danilo gets a block in. 31:51 Theo Walcott takes a shot. Save by Samir Handanovic. 30:48 The offside flag is raised against Antonio Di Natale. Direct free kick taken by Wojciech Szczesny. 30:24 Larangera Danilo restarts play with the free kick. 29:07 Robin van Persie has an effort at goal from just inside the box that misses to the right of the target. 28:54 Robin van Persie handles the ball and concedes a free kick. Kwadwo Asamoah takes the free kick. 28:30 Free kick taken by Wojciech Szczesny. 27:47 Foul by Robin van Persie on Emmanuel Agyemang-Badu, free kick awarded. Larangera Danilo takes the direct free kick. 25:24 Unfair challenge on Kwadwo Asamoah by Emmanuel Frimpong results in a free kick. Free kick taken by Kwadwo Asamoah. 24:38 Free kick awarded for a foul by Larangera Danilo on Robin van Persie. Johan Djourou takes the direct free kick. 22:29 Unfair challenge on Pablo Armero by Alex Song results in a free kick. The free kick is swung in right-footed by Antonio Di Natale, clearance by Johan Djourou. 22:12 Antonio Di Natale takes a shot from close in that hits the post. 20:59 Alex Song takes a long range shot harmlessly clearing the crossbar. 20:21 Antonio Di Natale takes a shot. Save by Wojciech Szczesny. 18:56 Mehdi Benatia is adjudged to have handled the ball. Free kick taken by Wojciech Szczesny. 18:03 Carl Jenkinson gives away a free kick for an unfair challenge on Pablo Armero. Antonio Di Natale crosses the ball from the free kick right-footed from left wing, Wojciech Szczesny makes a save. 17:37 The official flags Theo Walcott offside. Samir Handanovic takes the direct free kick. 16:39 The offside flag is raised against Kwadwo Asamoah. Wojciech Szczesny restarts play with the free kick. 14:13 Free kick awarded for an unfair challenge on Thomas Vermaelen by Antonio Di Natale. Direct free kick taken by Wojciech Szczesny. 10:29 Larangera Danilo concedes a free kick for a foul on Robin van Persie. Free kick taken by Robin van Persie. 9:07 Yao Gervinho takes a shot. Save made by Samir Handanovic. 8:41 The referee blows for offside against Antonio Di Natale. Wojciech Szczesny restarts play with the free kick. 6:35 Corner taken right-footed by Theo Walcott from the left by-line to the near post, Pablo Armero manages to make a clearance. 6:17 Aaron Ramsey takes a shot. Blocked by Larangera Danilo. 4:33 Emmanuel Agyemang-Badu takes a shot. Save made by Wojciech Szczesny. 3:17 Theo Walcott is caught offside. Indirect free kick taken by Samir Handanovic. 1:41 Theo Walcott takes a shot. Save by Samir Handanovic. 0:00 The referee gets the game underway. Live text and data provided by The Press Association.