Williams will race into another season with Valtteri Bottas alongside Felipe Massa.
The British team had options on both drivers for 2016, but it had been rumoured Finn Bottas was a candidate to switch to Ferrari, who ultimately re-signed Kimi Raikkonen.
Brazilian Massa’s seat, meanwhile, had been linked with a paying driver like Force India’s Sergio Perez, plugging a hole in Williams’ budget.
But Mexican Perez said at Monza on Thursday that he is staying at Force India.
“I think very soon things should be announced,” he said. “It should be announced hopefully before the next race.”
It had also been rumoured that Jenson Button might return to Williams, some 16 years after making his debut for the Grove team.
But team founder and boss Sir Frank Williams said: “Stability is key for any team to thrive in formula one, so to be able to enter a third season with one of the strongest driver lineups on the grid puts Williams in a fantastic position to continue its momentum towards the front of the grid in 2016.”