Walcott scored one goal and troubled Fenerbahce throughout
Arsenal consolidated their position at the top of Champions League Group G with a magnificent victory in Istanbul.
Emmanuel Adebayor slotted low to give Arsenal the lead and Theo Walcott rounded Volkan Demirel to make it two.
Fenerbahce replied when Dani Guiza's volley was poked into his own net by Mikael Silvestre but Abou Diaby fired the visitors into a 3-1 lead.
After Alex Song volleyed a fourth Guiza lobbed Manuel Almunia, but Aaron Ramsey came on and drilled a deserved fifth.
Ramsey replaced the superb Diaby on 73 minutes and provided a fitting end to a memorable evening for the north London club.
The Gunners were applauded off the field by the home supporters who, despite seeing their side's chances of reaching the knockout rounds suffer a potentially fatal blow, recognised a fine display of attacking football.
Arsenal are now two points clear of Dynamo Kiev after they beat Porto away from home to leapfrog the Portuguese side into second place.
Fenerbahce were undefeated in 15 European games at home but showed exactly why they are struggling in their domestic league with a series of woeful defensive errors.
Injuries to Bacary Sagna, William Gallas and Kolo Toure forced Gunners boss Arsene Wenger to include Emmanuel Eboue, Song and Silvestre in an unfamiliar-looking back four.
The quartet was exposed throughout a testing evening but a combination of poor Fenerbahce finishing and a number of superb saves by Almunia limited the damage.
At the other end Arsenal were at times unstoppable, their speed of thought and movement leaving the home midfield and defence chasing shadows.
Luis Aragones' men had been warned about Adebayor's threat when he wriggled free and shot over the cross-bar in the fifth minute.
And, five minutes later, Fenerbahce were punished for their failure to get tight to the Togolese striker, who collected Cesc Fabregas's precise through-ball and raced clear before coolly shooting past Volkan.
With the boisterous home crowd temporarily silenced, Arsenal went on the attack again and took full advantage of some more non-existent marking from their opposition.
In similar circumstances to Arsenal's opener, Fabregas picked up possession in midfield and provided a delicious slide-rule pass for Walcott to jig past Volkan and tap home.
Song celebrates scoring Arsenal's fourth goal with a fine volley
Fenerbahce might have been three goals down inside 13 minutes when Diaby beat Edu with an impressive piece of trickery on the right and crossed to the back post for Samir Nasri, whose shot was well saved by Volkan.
An unnecessary body-check by Song allowed the hosts a set-piece from which Guiza's volley across the face of goal was diverted past Almunia by Silvestre on his Champions League debut for Arsenal.
Fenerbahce were inevitably going to push hard for an equaliser but they were stung on the counter-attack as Diaby left Edu floundering and arrowed a low left-footed shot into the bottom right-hand corner.
Fenerbahce will feel unfortunate not to have narrowed the deficit by half-time after Semih Senturk was foiled by Almunia.
Guiza then had a strike correctly disallowed for offside, saw another shot zip inches wide and a third effort blocked by his compatriot in the Arsenal goal.
Arsenal began the second half with a series of flowing attacks and it was from one such movement that Lugano brought down Nasri on the left wing.
From Fabregas' resultant free-kick Silvestre nodded on for Song to lash into the bottom corner.
Following a pulsating opening two thirds, a temporary lull ensued but that was broken when Song failed to deal with Edu's long ball forward and Guiza finally got his goal.
But Arsenal would have the final say and Ramsey marked his first appearance in the Champions League proper with a venomous finish from the edge of the penalty area.
Arsenal manager Arsene Wenger:
"Because the two teams were going forward it was a very open game and Fenerbahce are an attacking side and are very dangerous going forward.
"Both teams were going forward 100% but the fact we scored an early goal forced Fenerbahce to come out and we caught them many times on the counter-attack.
"Our pace, movement and technique made the difference and allowed us to take advantage of it but it was not an easy game.
"I am very proud of the team. The average age was 23 and I am proud because we came in and tried to dictate the game in a very heated atmosphere.
"It is very pleasing that they seemed to play with no fear. I am pleased to see it works.
"We came here and had a go. We started strong, we remained quite strong and we finished strong."
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