The 26-year-old former Brighton & Hove Albion defender, who has enjoyed loan spells with Havant & Waterlooville, Eastleigh, Eastbourne Borough, Mansfield Town and the Cherries, for four months before signing in 2012, has been central to Bournemouth's rise in recent seasons.
He was one of three outfield players to play in every minute of every league game for the club this season and has in total made 231 appearances for Bournemouth, scoring 15 goals.
Upon signing his new deal, the Hastings-born centre-back told the club's official website: "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.
"Myself and AFC Bournemouth have been the perfect match. Since the manager came in, things have been forever moving upwards and that has matched my own ambitions.
"These are exciting times to be at the club and hopefully we can continue to have as much success as we have had in the last few years." Bournemouth manager Eddie Howe added that Cook was a big part of his plans for next season.He said: "This new contract is fully deserved after the season Steve has had."He has developed into an outstanding defender, has shown great consistency and has proved himself capable of playing at the very highest level."I am delighted Steve sees his long-term future at AFC Bournemouth because he is a major part of our plans going forward."