Dortmund have confirmed Christian Pulisic is joining Chelsea in a £58 million (€64m/$73m) deal that will see him loaned back to the German club for the remainder of the 2018-19 season.
The USA international attacker has impressed since making the breakthrough for the Bundesliga side during the 2015-16 campaign and has since made 115 appearances for the top team, scoring 15 goals and creating another 24.
He has, however, struggled to hold down a regular starting place in Lucien Favre's side as they have charged to the top of the league standings, where they have opened a six-point gap to Bayern Munich.