The 26-year-old centre-back played every minute of the Cherries' league campaign this season.
"It has always been my plan to stay here as long as possible, so to be given the chance to do that is really pleasing," he said.
Cook has made 231 appearances for the club since joining from Brighton in the summer of 2011.
"Myself and Bournemouth have been the perfect match," Cook added. "Since the manager came in, things have been forever moving upwards and that has matched my own ambitions."
Bournemouth defender Steve Cook has signed a new four-year contract with the Premier League club.