Turkish-German forward joins Fenerbahçe
In a statement, Fenerbahçe said they acquired the 26-year-old right winger from Italy's Genoa for three years, with the option of a further season.
The Istanbul team wished their new signing the best of luck for new achievements.
Gümüş was born in the German town of Pfullendorf but has Turkish citizenship as well.
He played for Fenerbahçe's city rivals Galatasaray from 2014-2019.
In his five-year term, Gümüş won eight trophies with the Lions, including three top-tier Super Lig titles in 2015, 2018 and 2019.
Last summer, he made his way to Genoa.
Gümüş has spent the second half of the last season in another Turkish club, Fraport TAV Antalyaspor, for which he scored five goals in 10 Super Lig appearances.
In early August, Gumus returned to Genoa once his loan deal at Antalyaspor ended.