Robert Kubica will leave Williams at the end of the Formula One season.
Polish driver Kubica this year featured in F1 for the first time since 2010, his career having been interrupted by life-altering injuries he sustained in a rally crash.
The 34-year-old has endured a dismal campaign with Williams, which failed to get its car ready for the start of pre-season testing in Barcelona.
However, Kubica scored the team's only point via a 10th-place finish at the German Grand Prix.
"I have taken the decision I will not continue with Williams after the end of the year," Kubica told a news conference ahead of the Singapore Grand Prix.
"It's a decision I took and this opens a bit opportunities for me in the future in different situations and now I will evaluate what is possible."
Team principal Claire Williams added in a statement: "I would like to thank Robert for his hard work and respect his decision to leave the team at the end of the 2019 season.
"Robert has been an important member of the team in both his role as reserve and development driver, and subsequently as one of our race drivers in 2019.
"We thank him for his continued efforts throughout what has been a challenging couple of seasons and wish him well in his future endeavours."
Kubica will evaluate all the opportunities available to him before making a decision on his future, but he hopes to remain in F1.
"I always said that it took a lot of energy, a lot of time for me to recover and come back to the sport. Since I came back to Formula One I would like to stay, I said this year it was a goal to remain in Formula One," he said.
"I think I have to bring back a bit of joy of racing for myself. This season has been very tough from a performance point of view but it has also been very demanding - being back in Formula One after a long time is not easy, especially in a difficult situation like we are.
"Still, I thank the team for the opportunity and I will see what the future will bring."