AS Roma have completed the signing of former Borussia Dortmund defender Mats Hummels on a free transfer, the Serie A club announced Wednesday.

Hummels left Dortmund at the expiration of his contract this summer. The 35-year-old spent 13 seasons with the Bundesliga side, making 508 appearances across two spells.

Details of the transfer were not revealed but Italian media reported the 35-year-old has signed a season-long deal for 2.5 million ($2.8 million).

After helping Dortmund to win Bundesliga titles in 2010 and 2011, Hummels signed for Bayern Munich, whose academy he came through, in 2016. Following three trophy-laden years at the Allianz Arena, he returned to Dortmund in 2019.

In his final season in Dortmund, Hummels was a key figure in the team's run to the Champions League final and started in the defeat to Real Madrid at Wembley.

Hummels has won 78 caps for Germany and was part of the 2014 World Cup-winning team but was left out of the squad for this summer's European Championship.

His arrival at Roma follows the departure of defender Chris Smalling to Saudi Pro League club Al Fayha earlier this week. Roma have begun the new Serie A season by taking just two points from three games.

Information from Reuters contributed to this report.