The 30-year-old joined the US-owned team from Alpine in 2025 and is currently 16th in the championship and 13 points behind British teammate Oliver Bearman.
Haas, the smallest team on the grid, are seventh of 11.
"My time with Haas F1 Team will come to an end at the end of the 2026 season. I leave this project with my head held high and proud of my performances in what were not always the easiest of circumstances for various reasons and factors outside of my control," said Ocon on social media.
"There are still many races to go this season and, as always, I will give it my everything behind the wheel for myself and for my team. I am still motivated. I am still hungry. This is absolutely not the end of my Formula 1 career."
Haas confirmed the departure in a separate statement thanking Ocon for his contribution.
The team have several candidates to replace Ocon, with Ferrari-backed Brazilian Rafael Camara one of the favourites.
Haas use Ferrari engines while also having close technical ties with Toyota.
Ocon's chances of getting another race seat are not great, with Red Bull-owned Racing Bulls and newcomers Cadillac yet to confirm their 2027 lineups but both having other options including retaining their existing drivers.
The Frenchman, a race winner with Renault-owned Alpine in Hungary in 2021, could switch to being a test and reserve driver and carried out that role for Mercedes in 2019 after losing his place at Force India (now Aston Martin).
The next race is the Bahrain Grand Prix in Malaysia this weekend.
