Gourcuff suffers adductor injury
The 28-year-old has been impressive for the Ligue 1 side this term - scoring four times in nine appearances in all competitions.
However, he is now facing a lay-off, with a return date for the former Milan and Bordeaux playmaker yet to be determined.
A statement from Lyon read: "Medical examinations taken of Yoann Gourcuff revealed a muscular injury along the right adductor.
"The treatment of this injury is the subject of a rigorous protocol on the part of the medical team of the club in order to allow Yoann to recover as soon as possible.
"The return date for Yoann will be determined later jointly by the medical staff and Yoann."
Lyon currently sit third in Ligue 1 and host Guingamp this weekend.