The French international joined the club from Ligue Un side Lorient two years ago and has established himself as a first choice centre half at the Emirates, racking up 85 appearances.
Manager Arsene Wenger said: The development Laurent has shown has been absolutely exceptional. Laurent has been outstanding for us over the last two seasons. I am very pleased he has decided to commit his future to the club.
No other player has racked up as many appearances for the Gunners in the last tow seasons than the 26-year0old and Wenger will be pleased that he has taken a different path to that of Robin van Persie.
Koscielny said: “I'm delighted to have reached agreement with the club. I have had a fantastic time here and look forward to an exciting future with Arsenal.”
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