“I will not continue with Williams after the end of the season,” the Pole said Thursday at the Singapore Grand Prix.
Kubica made a return to F1 with Williams after a serious injury at the Ronde di Andora rally in 2011 in which his right forearm was partially severed.
In November last year, Kubica was announced as a Williams driver for 2019.
However, the 34-year-old has taken only one point after 14 races this season.
“Definitely it has been the biggest achievement of my life to come back,” Kubica said. “To go through what happened and still manage to race. Being back on the F1 grid was the best outcome I could imagine.” (AFP)