The 24-year-old Mendy, a product of Paris Saint-Germain’s youth system, made his France debut against Uruguay last year.
“I’m very proud and honored to sign for the biggest club in the world, and to link up with a manager who will help me progress,” said Mendy.
“I would like to thank Lyon, the president, the staff, the fans and all my teammates from these past two years. I wish you all the best.”
Only last week Real announced the signing of Belgian playmaker Hazard from Chelsea for a reported fee of €100 million ($113 million), while striker Jovic is another of the club’s recent acquisitions after signing from Eintracht Frankfurt for €60 ($68 million).
Spanish champion Barcelona has already signed 22-year-old midfielder Frenkie de Jong from Ajax.
Hazard and de Jong are currently the most expensive transfers of the summer window, along with center-back Lucas Hernandez who has moved from Atletico to Bayern Munich for a fee of €80 million ($90 million).