The Gunners began talks with Koscielny, 26, earlier this month, with manager Arsene Wenger having made keeping the centre-back at the club one of his summer priorities.
France international Koscielny arrived at the club from Lorient in summer 2010, establishing himself as one of the Gunners’ key performers and starting 85 games.
Wenger said he was delighted to have secured the defender’s signature, hailing him as a player who “has been outstanding for us over the last two seasons”.
“When you consider that, until 2009, he was playing in Ligue 2 in France and that he is now performing at the very top level in the Premier League and for his country, the development that he has shown has been absolutely exceptional,” he added.
“Laurent is a top-class player and I am very pleased he has decided to commit his future to the club.”
Koscielny said: “I am delighted to have reached agreement with the club. I have had a fantastic time here and look forward to an exciting future with Arsenal.”
Koscielny has won four caps for France, and played the full 90 minutes in their Euro 2012 quarter-final defeat to Spain. His impressive form had seen him linked with moves to Inter Milan and Barcelona, although it is not thought either club made a firm inquiry.
- Analysing Laurent Koscielny and his comparison with Kompany (footballonlineworld.com)
- Barcelona Target Arsenal Centre-Back Laurent Koscielny as Nou Camp Boss Looks to Strengthen Defence (caughtoffside.com)
- Kos he’s worth it: Arsenal open talks with Laurent Koscielney over new five-year deal (mirror.co.uk)
- Arsenal open up contract talks with Frenchman (footballfancast.com)