The Belgium defender left Manchester City this week to sign OL in a permanent deal.
Genesio said: "Recruitment is always a difficult job. We've been following Jason for three years. This year we finally had the opportunity to bring him here. It was a work of patience and I am very happy that this transfer is realised."
Denayer also stated: "It was for me a desire to come to Lyon that did not date from today. The discussions were much further than before, it was in my head for several years. The club and staff have been following me for a long time and know me, it's important for me.
"I have good athleticism and good footwork. I feel comfortable right and left and I will make sure to adapt to the will of the coach."