The 28-year-old, who moved from Brighton to Everton in 2022, has one goal in 32 games for the Toffees.
The Frenchman scored eight goals in 31 games while on loan at his previous team, Brentford, during the previous campaign.
As he approached the last year of his contract at Goodison Park, Maupay has not appeared in the first two Premier League games this season for Everton.
Maupay will now reside in France and work with former Brighton manager Roberto de Zerbi.
This summer, the team also signed Pierre-Emile Hojbjerg and Mason Greenwood.
In the summer transfer window, Everton signed Tim Iroegbunam, Iliman Ndiaye, and Jake O’Brien.
Before the transfer window ends, the Toffees seek to finalize a loan agreement for 26-year-old Lyon midfielder Orel Mangala.
