Manchester City's Premier League title challenge suffers major blow as Arsenal claim all three points at the Etihad Stadium.
Much had been made of Arsenal's inability to beat the big clubs in the top flight ahead of Sunday's encounter, but Arsene Wenger's side proved it is no soft touch with an impressive display to consign City to a first defeat in 15 games.
Cazorla opened the scoring from the penalty spot in the first half after returning City captain Vincent Kompany was adjudged to have blocked off Nacho Monreal.
City, which also welcomed leading scorer Sergio Aguero back into the starting lineup, was devoid of ideas going forward in the first half but was far more threatening after the break.
The defending champion was unable to pull off a fightback, though, and there was no way back when Cazorla turned provider with a free kick that was headed home by Giroud.
Defeat for City was the club's second at home in the league this season and a first loss since back in November ensured Manuel Pellegrini's side remains five points behind Chelsea, with the two teams set to face each other next in the Premier League.
Arsenal has now won five of its last six games and leafrogs arch rival Tottenham into fifth place.
Aguero made his first start for six weeks and Kompany was also back in the City starting lineup along with James Milner.
There were two changes to the Arsenal starting lineup following victory over Stoke City last weekend, with Aaron Ramsey and Hector Bellerin in for Tomas Rosicky and Mathieu Debuchy.
City made a positive start and Aguero was unable to pick out a teammate from the by line after referee Mike Dean played an excellent advantage when Laurent Koscielny clattered into Fernandinho with a clumsy challenge that resulted in a yellow card for the Frenchman.
It was Arsenal which was in front after 24 minutes, though, when Kompany tangled with Monreal after the fullback played a neat one two with Giroud and, although Joe Hart guessed the right way, he was unable to keep out Cazorla's precise penalty.
City looked short of ideas going forward as a frustrated David Silva was unable to make his presence felt and Aguero was starved of service.
Pellegrini reacted to City's lackluster first-half display by replacing Milner with Stevan Jovetic at halftime and Aguero came close to an equalizer just after the break when his deflected strike was only just off target.
The home side was posing far more of a threat to the Arsenal defense and Jesus Navas' drive was beaten away by David Ospina before Fernandinho's strike was deflected over.
The game was being played at a frantic pace and Koscielny then got a crucial touch on Navas' cross to divert the ball for a corner as Aguero was poised to turn it into the empty net.
City was left with a mountain to climb when an unmarked Giroud punished some poor defending by nodding in Cazorla's free kick after 67 minutes to stun the home fans.
Mathieu Flamini ought to have provided another goal for Giroud late on, but Kompany got in the way of his attempted pass as Arsenal saw out the game with ease.