Stoffel Vandoorne will leave McLaren at the end of the Formula One season.
The Belgian, who joined the team's young driver programme in 2013, made his debut as a deputy for Fernando Alonso at the 2016 Bahrain Grand Prix.
It was announced last month that two-time world champion Alonso will leave F1 at the end of this season, and news of Vandoorne's impending departure will intensify speculation that Racing Point Force India's Esteban Ocon will team up with Carlos Sainz Jr at McLaren next year.
Last week, Sauber dismissed reports that they were in talks with Vandoorne, who has managed to pick up eight points this season.
"I'm very grateful to McLaren for investing their faith in me over the past five years. I joined McLaren as a young driver and have since seen my career progress within the team from test and development driver to reserve driver and then to full-time race driver," said Vandoorne.
"While we haven't achieved the success we'd all hoped for, I've really enjoyed the past two seasons racing for McLaren and I have a great relationship with everyone in the team.
"My time at McLaren has been a great chapter in my career and I'm thankful for the opportunity the team, Shaikh Mohammed bin Essa Al Khalifa and Mansour Ojjeh have given me to gain valuable Formula One experience and develop as a driver.
"I intend to give it my all for the remaining seven races of this season and will announce my plans for next season in due course."
McLaren Racing CEO Zak Brown said: "It's clear we haven't provided Stoffel with the tools to show his true talent, but throughout our relationship he's proved to be a fantastic team player.
"His work ethic is impressive, he has a great reputation within the team and we've really enjoyed working with him. Of course, we would have loved to achieve more success during our time together, but that doesn't detract from the fact that he will always be a part of the McLaren family of grand prix drivers."