He is the second player to join Villa this month after Philippe Coutinho made his loan from Barcelona permanent.

"I am delighted that we have been able to attract one of the most promising young talents in European football," said Villa boss Steven Gerrard.

"We have a very clear plan to make our team stronger and Bouba is an important part of that."

Kamara made 170 appearances for Marseille after graduating from the club's academy in 2016, helping the club reach the Europa League final in 2018 and finish runners-up to Paris Saint Germain in Ligue 1 this season.

He has nine caps for France U21s and has been called up to the senior squad for the first time for Nations League matches against Denmark, Austria and Croatia next month.