Steve Cook scored 21 goals for the Cherries.
Steve Cook has signed for Forest on a two-and-a-half-year deal.
Cook is one of Bournemouth's longest-serving players and has made over 400 appearances for the club.
He joined the Cherries on loan in 2011.
Cook told Forest's website that it was the perfect time to make the move.
The club is making progress and I'm excited for the new challenge.
Cook missed the start of the Championship campaign because of a knee injury and has only appeared in four other games.
The defender is Forest's second signing of the January transfer window, following the loan signing of Keinan Davis.
Steve is a fantastic player and brings a good level of experience, both in the Championship and the level above, as we feel this is an important signing.
He's played for a team that has won a lot of games.
Cook helped the Cherries to promotion from League One to the premier league for the first time in the club's history in 2015.
Bournemouth have confirmed that he will receive a testimonial game at the end of the season, after he was made club captain last season.
Cherries chief executive
He has been a key part of this club's success over the last 10 years and has played a pivotal role in some of the most memorable moments in our history.
The return of Harry Arter from a loan spell at Charlton Athletic has been confirmed by Forest.
On our dedicated page, you can find all the latest football transfers.
