The court in the southern city of Nîmes also ruled that 36-year-old Robert Plant should not be eligible for parole for 20 years.
Plant was formally charged in 2013 for the murder of 34-year-old Jouda Zammit, whose partially clothed body was found on January 24 of that year. She went missing after going jogging.
Her throat had been slit and her body and face disfigured with stones and a cutter.
Plant lived with his mother just yards from where the woman's body was found.
Nimes prosecutor Stephane Bertrand had sought a life term for Plant, dismissing arguments that he “had lost contact with reality” on the day of the murder.
Plant had been described by neighbours as “peaceful” but Bertrand described him as a “pervert” and “not a madman” who had “committed a particularly brutal crime.”
The victim had three children who are now aged 14, 11 and seven.