The 23-year-old midfielder moves to Ligue 1 after a near three-year spell at Crystal Palace.
Originally joining from VfB Stuttgart towards the end of the January transfer window in 2023, Ahamada made 31 senior appearances for the Eagles.
He made his debut as a second-half substitute for fellow midfielder Cheick Doucouré away to Manchester United in February 2023, the first of 28 Premier League appearances.
The midfielder spent last season on loan with Rennes, but now returns to France in a permanent move.
Everyone at Crystal Palace wishes Naouirou the best of luck with the next chapter of his career.