Santi Cazorla and Olivier Giroud struck in each half as Arsenal stunned lacklustre champions Manchester City 2-0 at the Etihad Stadium.
Cazorla converted a 24th-minute penalty and Giroud headed home from a set-piece with 67 minutes gone to put a dent in City's Barclays Premier League title defence.
City, despite the return of Sergio Aguero, created little in what was a generally dull game and the result left them five points behind leaders Chelsea with a trip to Stamford Bridge to come in a fortnight.
Arsenal's victory put aside their well-documented recent struggles against top-four opponents and considerably enhanced their prospects of finishing in the Champions League positions this term.
The Gunners were thrashed 6-3 in the corresponding fixture last season and the odds again seemed against them as Aguero and Vincent Kompany returned to the City starting line-up.
But Aguero, who played up front alone in the first half, had a quiet game and City struggled to get anything going even though they dominated possession.
Arsenal looked the more incisive at times and fit-again captain Kompany was made to look rusty.
Kompany's defensive partner Martin Demichelis also had some moments of uncertainty and Arsenal went close to taking the lead from one of them.
Alex Oxlade-Chamberlain seized on a weak Demichelis header and burst down the right before whipping in an inviting cross for Giroud but the Frenchman glanced his header wide.
The Gunners broke through five minutes later as Nacho Monreal attempted to play a one-two with Giroud and was impeded by Kompany as he continued his run into the box.
The Spaniard may have gone to ground easily but referee Mike Dean was in no doubt about the contact and Cazorla took full advantage from the spot.
City were unable to muster a dangerous response despite controlling plenty of the ball.
One good Pablo Zabaleta break yielded nothing and Aguero was off-target with a header from a James Milner cross.
Kompany's frustrating afternoon continued as he was booked for a heavy challenge on Giroud.
City boss Manuel Pellegrini reverted to his default 4-4-2 set-up after the break as Stevan Jovetic replaced Milner and moved alongside Aguero.
The change of approach initially appeared to work and Aguero had their first serious shot with an effort that deflected wide. Jesus Navas was the first to test David Ospina, the deputy keeper again preferred to Wojciech Szczesny, with a powerful effort that was parried away.
But the game also opened up and Sanchez curled an effort across goal after turning Zabaleta out wide. Dean then overlooked two possible fouls on the edge of the City area as a chance opened up for Aaron Ramsey on his return to the side but the Welshman shot over.
City produced another good move but Laurent Koscielny made a vital interception as Navas fired a cross in Aguero's direction.
Arsenal applied the killer touch after 67 minutes after Sanchez was fouled by Jovetic. Cazorla clipped a free-kick into the area and Giroud reacted quickest, losing his marker Fernando to head home in simple fashion.
It was not dissimilar to an Everton equaliser which also cost City points last week and the defending of set-pieces could be a concern.
Sanchez threatened another with a powerful strike from the edge of the area but Joe Hart saved well.
City tried to hit back and Monreal cleared unconvincingly over his own bar but the hosts did not consistently trouble their visitors.
Arsenal efficiently and professionally played out the remainder of the game as City, despite the introduction of Frank Lampard, lacked inspiration.
As in previous years, it appeared the absence of Yaya Toure due to the African Nations Cup had proved costly and City will be anxious to raise their levels when they face Chelsea.
JOE HART : Almost got a hand to Santi Cazorla's penalty and could do little about Olivier Giroud's header from point-blank range. 6/10
PABLO ZABALETA : Fared relatively well keeping Alexis Sanchez quiet in the first half. Was only beaten by the Chilean on a couple of occasions. 6
VINCENT KOMPANY : A bit unlucky to concede a penalty but was still poor throughout. Took frustration out on Giroud in the 41st minute and was rightly booked. 5
MARTIN DEMICHELIS : Failed to keep Giroud quiet. Lack of pace a problem for City. 5
GAEL CLICHY: Failed to have any impact against his former team. 5
FERNANDINHO: Surprisingly substituted in the second half. Was City's best player. Surging runs from deep made City look dangerous. 7
FERNANDO: Sub-par. Lost Giroud for second goal and failed to keep Cazorla quiet. 5
JESUS NAVAS : Stung David Ospina's hands with a powerful drive but otherwise ineffective. 6
DAVID SILVA : Very, very quiet. Failed to provide the spark City needed. 5
JAMES MILNER : Performed poorly back in midfield. Only contribution was two wayward crosses. 5
SERGIO AGUERO : Still short of match-fitness. Lacked power and pace. Only had a few, poor attempts at goal. 6
STEVAN JOVETIC (on for Milner, 45mins): Gave City a bit more presence up front but still unable to unlock away defence. 6
FRANK LAMPARD (on for Fernandinho, 62mins): Also failed to swing the game in City's favour. 5
EDIN DZEKO (on for Navas, 76mins): Last throw of the dice for Manuel Pellegrini. Did not test Ospina. 5
DAVID OSPINA : Relatively assured performance. Not tested until 46th minute. 6
HECTOR BELLERIN: Showed maturity beyond his years in keeping Navas quiet. 7
PER MERTESACKER: Big German kept Aguero in check and looked confident throughout. 7
LAURENT KOSCIELNY : Vital deflection to deny Aguero in 60th minute. Booked. 7
NACHO MONREAL: Looked poor going forward at the start but improved as the game wore on and won the penalty that put Arsenal ahead. 7
FRANCIS COQUELIN : Solid and workmanlike in front of the back four. Wise decision from Wenger to select him ahead of Mathieu Flamini. 7.
AARON RAMSEY : Blazed over a good chance in the second half but otherwise just about good enough. 6
SANTI CAZORLA : Scored a perfectly-placed penalty to put Arsenal ahead and sneaked into the pockets between City's midfield and defence well. Masterful trickster. 8
ALEX OXLADE-CHAMBERLAIN : Put a good cross in for Giroud and worked tirelessly throughout. 7
ALEXIS SANCHEZ : Failed to score but caused City problems with his movement and trickery. Outshone Aguero in the battle of the South American stars. 8
OLIVIER GIROUD : Clinical header to seal the win. 8
TOMAS ROSICKY (on for Oxlade-Chamberlain, 65mins): Calmed things down in midfield as City pushed for a goal. 7
KIERAN GIBBS (on for Sanchez, 83mins): No time to make an impact. 6
MATHIEU FLAMINI (on for Ramsey, 83mins): Brought on to waste time and add fresh legs to the Arsenal team. 6
West Ham 3-0 Hull City
Hammers striker Andy Carroll said his side were eyeing European football after he scored the opener against Hull.
Second-half goals from Carroll, Morgan Amalfitano and Stewart Downing secured all three points for the east London club following a run of four games without a win.
Asked if West Ham could qualify for Europe, England striker Carroll said: "There's a belief in the dressing room, I don't see why not."
Hull were punished for failing to take their chances and this defeat left them in the relegation zone.
Frustrated Hull manager Steve Bruce said: "The way we played in the first half delighted all of us connected with Hull but in my experience you have to score.
"For all the good work we did, it unravelled really. You can't let them off the hook like that."