Lyon and Monaco have agreed the swap between Sebastien Squillaci and Sylvain Monsoreau.
Squillaci has signed a four-year deal at Stade Gerland after agreeing personal terms and passing a medical.
French international Squillaci is exited at the prospect of playing for the champions.
"When a club of this size shows an interest, there was no hesitation on my part," Squillaci told the club's official website.
"Competition in defence? It's part of the game which exists at all the big clubs.
"It is up to me to perform and to secure my place in the first team."