He signs from French club Lille for a fee of US$8.2m.
The 27-year-old is set play alongside his compatriot Dany Nounkeu in defence at Galatasaray, the duo are currently training with the national side ahead of a friendly against Ukraine on Sunday.
Chedjou played 154 Ligue 1 games for Lille after joining from FC Rouen in 2007, helping the northern club clinch the French title two years ago.
Cameroon defender Aurelien Chedjou has joined Turkish champions Galatasaray on a four-year deal.