This week marked 20 years since Wenger’s appointment and this win over their local rivals was a most memorable match to celebrate the milestone.
Arsenal exploited lackadaisical Chelsea defending to score three times in the first half as they claimed a first league win over their London rivals since a 5-3 triumph in October 2011.
It was Arsenal’s biggest league win over Chelsea since April 1997 and their most handsome home victory against the west London club in 26 years.
Arsenal climbed to third place in the Premier League table, five points below leaders Manchester City, after registering four successive league wins for the first time in over a year.
Antonio Conte’s Chelsea, whose side have now gone three league games without a win, slid to eighth, the optimism engendered by their three opening victories now almost a distant memory.
Wenger made 11 changes to the second-string team that had won 4-0 at Nottingham Forest in the League Cup and his big guns fired immediately, Santi Cazorla stinging Thibaut Courtois’s palms.
Arsenal went in front in the 11th minute courtesy of an embarrassing error by Gary Cahill that left him hiding his face in his hands.
Forty yards from goal, the England centre-back allowed himself to be robbed by Sanchez, who surged into the box before clipping a lovely finish over Courtois for his fourth goal in three games.
It was Arsenal’s first league goal against Chelsea in seven games and within three minutes they had another.
Fabregas withdrawn
A slick passing combination culminated in Alex Iwobi intelligently picking out Hector Bellerin on the right-hand side of the box and the Spaniard’s low cross was swept home by Walcott.
Briefly, hope flickered for Chelsea. Willian drilled a shot narrowly wide and Arsenal’s rhythm was disrupted by the loss of Francis Coquelin to an apparent knee injury, with Granit Xhaka coming on.
But with the visitors pushing forward, Arsenal hit them with a clinical counter-attack five minutes before half-time.
Ozil threaded a pass wide to Sanchez and then hared into the box to meet the Chilean’s lofted cross with a volley that skidded off the deck and looped over Courtois into the net.
Cesc Fabregas had returned to the Chelsea starting XI after his mid-week League Cup brace at Leicester City, but the former Arsenal skipper was withdrawn nine minutes into the second half.
Marcos Alonso took his place as Conte reconfigured his team in a 3-4-3 formation.
It helped Chelsea stop the rot, but they never threatened to force their way back into the game and Courtois had to spread himself at his near post to prevent Walcott netting a second goal.
When Chelsea did get in behind, substitute Pedro Rodriguez racing clear after Diego Costa had picked Laurent Koscielny’s pocket, Bellerin sprinted back to produce an impeccable recovery tackle.
Chelsea did not oblige their former goalkeeper Petr Cech to make a save until the closing stages.
He saved comfortably from Cesar Azpilicueta’s curler, but then had to scramble from his line alertly to block from substitute Michy Batshuayi.