Williams will field an unchanged race driver lineup in 2015.
The news, announced by the British team early on Sunday, ends speculation Finnish sensation Valtteri Bottas could be scooped up by a grandee team like McLaren.
And there had been rumours in the past days that Brazilian Felipe Massa, who joined the team from Ferrari this season, might be replaced by his well-sponsored countryman Felipe Nasr for 2015.
Nasr is currently Williams' third driver, but the Grove team said in its statement on Sunday that the 2015 reserve will be announced "in due course".
"Felipe and I have a good working relationship," said Bottas, "and this early announcement will help us both input into the ongoing development of the FW36 and the FW37."