Williams has confirmed that Felipe Massa will race for the team in 2014, alongside current driver Valtteri Bottas.
Massa joins the team after spending eight years with Ferrari and will replace Pastor Maldonado.
Bottas made his debut for Williams at the start of 2013, having spent 2012 as the team's reserve driver.
"Williams is one of the most successful and important teams of all time in Formula One," said Massa.
"When I was a kid, I always dreamed about racing for Williams, Ferrari or McLaren and I'm glad to be signing with another icon of the sport following my time at Ferrari."
"It is also nice to remember that some of the best Brazilian drivers raced for Williams and cemented a strong national link with the team. With such a major change of regulations in 2014, I hope my experience will be useful in helping the team in its effort to move on from a difficult period."
"Since my early days in motor racing, I don't remember seeing so many new rules in a single season and I'm fully prepared to work with everyone at Grove to make sure we find the right direction. I'm highly motivated to start working hard from the very beginning in what is an exciting new challenge in my career."
Bottas added that he was eager to have Massa as his 2014 team-mate.
"I'm very happy to be staying with the team as I embark on my second season in Formula One," he said.
"I have known everyone here for many years, firstly as a test driver and now as a race driver, so it feels like home. I have faith in Williams and I know we can do so much better in the future than our current performance shows."
"I am looking forward to having Felipe as my teammate. He is a quick and experienced driver and together we will be pushing to the maximum to improve the car and get as many points as we can next season. We will be working throughout the winter to ensure we are ready for the challenge of 2014."
Team principal Sir Frank Williams expressed his delight at the line-up.
"He [Massa] is an exceptional talent and a real fighter on the race track; he also brings a wealth of experience as we begin a new chapter in our story."
"Valtteri is a valued member of the team and I'm pleased he was able to demonstrate his talent in tricky conditions in Montréal. There is much more to come from him."
