Lyon confirmed they have completed the signing of left-back Aly Cissokho from Porto for €15m.
Cissokho, 21, penned a five-year deal with the deposed French champions after passing a medical today.
A clause has been included in the deal which will entitle Porto to 20% of any future transfer fee should Lyon sell Cissokho.
The Frenchman, who came close to signing for AC Milan earlier this summer, is Lyon's third close-season signing, after striker Lisandro Lopez and left-winger Michel Bastos.
Cissokho will train with his new team-mates for the first time on Monday.