Man City face FIFA probe over Jeremy Helan deal
Hélan, who is 17, joined City in February and Rennes want Fifa to look into the Premier League club's conduct.
"We have referred this to Fifa," the technical director, Pierre Dreossi, told the Independent.
City are understood to be adamant that they broke no rules in bringing the player, who was then 16, to the club.
Rennes' action comes after Chelsea were given a transfer ban to 2011 by Fifa after being found guilty of illegally inducing Gaël Kakuta to sign from Lens. Chelsea have said they did nothing wrong and that they will appeal.