Mats Hummels has told Borussia Dortmund he wants to join Bundesliga champions Bayern Munich, a statement on the official BVB website has confirmed.
The Germany international's future has been in doubt amid strong links with a switch to Munich in the summer.
Hummels, 27, began his career at Bayern but left the club as a 19-year-old in 2008.
The Dortmund statement said: "Defender Mats Hummels has communicated his desire to leave the club in the summer and wants to join league rivals Bayern Munich for next season."
It added that Bayern had yet to make an offer for Hummels and stressed: "With Mats Hummels -- as at present with all other players from Borussia Dortmund -- no exit clause has been agreed, and the player is under contract to June 30, 2017."
Dortmund captain Hummels had previously said he was losing sleep as he tried to decide whether to stay or leave, and both clubs had confirmed that a transfer to the Allianz Arena was an option.
According to media reports in Germany, Bayern are ready to offer Hummels a four-year deal.
The two clubs will meet in the last domestic match of the 2015-2016 season when they contest the DFB Pokal final in Berlin on May 21.
Dortmund CEO Hans-Joachim Watzke said earlier that Hummels would captain BVB in that match.