Chelsea have loaned out Ghana Black Stars defender to Bundesliga club Schalke 04 for the 2016/2017 season.
The Premier League club confirmed the move on their official website on Tuesday.
"Baba Rahman has today joined Schalke on a season-long loan," Chelsea announced.
"The move is a return to the Bundesliga for the Ghanaian left-back who signed for Chelsea from Augsburg a year ago.
"Last season he made 23 appearances, 19 of them starts, with his debut also his first career game in the Champions League, a 4-0 win over Maccabi Tel Aviv."
Rahman, 22, was signed by Jose Mourinho last season but the Ghana star had little playing time as right-footed Cesar Azpilicueta was preferred at left-back.