The Frenchman has spent the last four years in London and this season developed a strong partnership with Per Mertesacker at the heart of Arsenal's defence.
The 28-year-old, who was signed from Ligue 1 side Lorient, has contributed to 15 clean sheets in his 31 Barclays Premier League appearances this season as Arsenal secured fourth place and reached the FA Cup final. "I have enjoyed four great years already and I look forward to continuing to help the team," said Koscielny.
The news was welcomed by manager Arsene Wenger too. "Laurent has proven himself to be an outstanding player since joining us in 2010," he said.