The 20-year-old has secured a move to Stade Velodrome on what is believed to be a five-year contract.
Marseille has signed midfielder Georges-Kevin N'Koudou from Ligue 1 rival Nantes.
The 20-year-old broke into the first team at Nantes in the 2013-14 season and became an integral part of the side last term as Michel Der Zakarian's men finished 14th in the table.
The length of N'Koudou's deal has not been made public, although widespread reports in France suggest the midfielder has been handed a five-year contract.
N'Koudou made 32 appearances in all competitions in 2014-15, scoring twice, and will now look to stake a claim for a place in a Marseille midfield that is reported to be set to lose Giannelli Imbula to Inter.