Former Netherlands international Nigel De Jong signed a short-term deal with Mainz on Friday.
The 33-year-old will return to the Bundesliga for the first time since 2009, when he left Hamburg for Manchester City.
Since then, he has played for AC Milan and the LA Galaxy until signing a two-year deal with Galatasaray in August 2016. After appearing in 24 games last season, he has not played at all this season
"I like Mainz's story, the club has established itself in the Bundesliga off its own back," De Jong said in a statement. "I want to help the team and the club achieve its aims this season and I can only thank Sandro Schwarz and Rouven Schroder for giving me the chance here. I'm really pleased to be back in the Bundesliga, one of Europe's top leagues."
Mainz are two points above the relegation zone in the Bundesliga at the halfway point in the season and will hope De Jong provides a boost after the departure of Fabian Frei to Basel.
"Nigel is a leader and a fighter, but has a cool head and is very professional," Mainz sporting director Schroder said. "He's going to help the team with his experience and give us a real boost ahead of the second half of the season. We're really pleased to bring in a player of his quality."