We Love Green festival at the Bois de Vincennes in the east of Paris in June,
Bjork was confirmed as the other headline act a few weeks ago, making her only 2018 appearance in France on Sunday June 3.
Orelsan has a French tour in 2018, but it has already widely sold out including two dates at the Bercy arena in Paris in March.
Orelsan's La fête est finie was one of 2018's most significant releases, marking the rapper's return as a solo artist after his success as part of the Casseurs Flowters duo.
Last summer We Love Green featured Justice, Solange and Benjamine Clementine, the two day event hosting three stages of musical acts, others hosting events including talks, films and debates that reflect the environmentally aware tone of the event.
We Love Green 2018 is being held on the weekend of June 2 and 3 and tickets are already on sale.