Mats Hummels has completed his return to Borussia Dortmund, the club have confirmed.
A deal with Bayern Munich for Hummels was struck earlier this month and the transfer has gone through after he passed his medical and signed his contract on Friday.
Dortmund, who finished second in the Bundesliga to Bayern last term despite leading the table for much of the season, have not disclosed the contract length.
They are reported to have paid a €38million fee to bring Hummels back to Dortmund after he spent the last three seasons in Bavaria.
He could make his latest Dortmund debut against Bayern in August's DFB-Supercup, with BVB then opening their Bundesliga campaign at home to Augsburg.
Dortmund are away to Bayern in November before hosting the defending champions at Signal Iduna Park in the closing weeks of the season.
