Kagawa had started one Bundesliga game this term for Dortmund, who currently hold a six-point lead on second-place Bayern Munich
Shinji Kagawa will join Beşiktaş on loan for the remainder of the season.— Borussia Dortmund (@BlackYellow) January 31, 2019
We thank him for his effort, class, and undeniable influence on BVB and the Bundesliga. pic.twitter.com/QFVQgsYVGc
"Shinji is not only an outstanding football player, but also a great friend of our club," said Dortmund's sporting director Michael Zorc. "We did not want to deny him this request."
Kagawa had previously stated his preference to play in Spain, a league suited to his ability on the ball, but the Japan star will now move to Turkey to join the Super Lig side.
Besiktas are sixth in the table despite taking four points out of a possible six since the Super Lig's mid-season break.
Next up for Besiktas is a match with Bursaspor on Sunday.