Marseille completed a move for Montpellier midfielder Morgan Sanson on Wednesday (AEDT) in a deal which could rise up to $17 million.

The 22 year-old was in his fourth season at Montpellier but the Frenchman makes the switch after the clubs agreed a deal of $12.7 million, plus $4.2 million in bonuses.

Marseille president Jacques-Henri Eyraud was thrilled to welcome Sanson, a France youth international.

"I am very pleased that the first player who joined us during this transfer window is one of the most promising talents in French football," he said. 

"We also want to rely on young players who will accompany our project until we reach our goals."

Marseille is sixth in Ligue 1 but a distant 15 points behind leader Monaco and Nice.

Sanson had contributed three goals and six assists in 20 league games for Montpellier this season.