Williams founder Sir Frank Williams says that retaining Felipe Massa and Valtteri Bottas for a further season provides the outfit with stability.
Williams will keep the same line-up for a third successive campaign, the first time it has done so since Juan Pablo Montoya and Ralf Schumacher raced for the team between 2001 and 2004.
"Stability is key for any team to thrive in Formula 1, so to be able to enter a third season with one of the strongest driver line-ups on the grid puts Williams in a fantastic position to continue its momentum towards the front of the grid in 2016," he said.
"Felipe’s blend of experience and raw speed is a rare attribute in Formula 1. Felipe thrives in an environment where he is valued and can build a long-term relationship and we are delighted that he has become such an important part of the Williams family.
"Valtteri has become such a staple of Williams that we are as excited about the prospect of his potential as a championship contender as we are about returning the Williams name to the top of Formula 1.
"Felipe and Valtteri quickly developed an exceptional working relationship from the beginning of 2014 and, while they remain fiercely competitive as rivals, they have always recognised the value of their collaboration in driving the team up the grid.
"Their shared work has given the technical team at Williams the best possible guidance in how to deliver the performance needed to carry the team forward, and both drivers have played a pivotal role in the rejuvenation of Williams.
"The successes we’ve enjoyed over the past two seasons would not have been possible without them, and they will play an essential role in the targets we aim to deliver in the future."