The 21-year-old is set to spend the season with the Turkish side, who have an option to sign him permanently thereafter, as reported by the club's official website.
Fofana's move comes just two days after a proposed loan switch to AEK Athens collapsed late on.
The clubs remained in disagreement over several points, which meant that the transfer couldn't take place.
Fofana, who has been capped by Ivory Coast at senior level, signed for Chelsea in January 2023 but isn't part of manager Enzo Maresca's plans.
Fofana made four appearances for Chelsea after joining and subsequently had loan spells at Union Berlin and Burnley.
Fofana, who joined Chelsea in January 2023, spent time on loan at Burnley last season
He scored four goals in 15 appearances for Burnley in the Premier League in the second half of last season.
Chelsea were eager to secure a move for Fofana given the large amount of players at the club.