Trab bring Altintop to Turkey
The 28-year-old, whose twin brother Hamit joined Real Madrid last month, was born in Germany and has played his entire club career there, having represented Kaiserslautern, Schalke and most recently Eintracht Frankfurt.
Following Frankfurt's relegation from the Bundesliga, he has now chosen a three-year deal with the Black Sea club.
Trabzonspor have won the national championship six times, most recently in 1984. They finished second last season behind Fenerbahce and go into the third qualifying round of the UEFA Champions League.