The "Les Bleus" international is expected to undergo a medical in West London on Friday and sign a contract until 2032. Chelsea will reportedly pay approximately £52 million for the new signing, according to The Athletic.
The 26-year-old defender featured in 55 matches last season and was a consistent starter under manager Oliver Glasner.
He played the full match in last August's FA Community Shield triumph against Liverpool and also in May's successful Conference League final against Rayo Vallecano. He was instrumental in helping the club secure its first European trophy and has been a key player for the team over the past two seasons.
His performances also earned him a call-up to this year's World Cup, where he made three appearances for France.