Chelsea have confirmed the arrival of the defender on a six-year deal from the Ligue 1 side.
Chelsea have splashed out once again by bringing in Axel Disasi from Monaco.
However, the defender arrives to boost Mauricio Pochettino’s backline.
He has been welcomed to Stamford Bridge by co-sporting directors Laurence Stewart and Paul Winstanley.
“Axel has showcased his quality over several seasons in France and that has deservedly led to recognition on the international stage,” they told the club’s official website.
“He is ready to take the next step in his career and we are delighted that will be with Chelsea.
“We welcome him to the club and look forward to him joining up with Mauricio Pochettino and his new teammates in the days ahead.”
However, Chelsea have moved for Diasi after losing Wesley Fofana to a serious knee injury that is expected to keep him out of action for a lengthy spell.
Also, the Blues had also waved goodbye to Cesar Azpilicueta and Kalidou Koulibaly this summer, meaning a new centre-back was needed.
Diasi will hope he can cement a regular place in Pochettino’s starting XI following his move.