Mercedes has confirmed the long-awaited news that Valtteri Bottas will partner Lewis Hamilton at the team this year, ending the Finn’s four-year stay at Williams, and completing the squad's 2017 driver line-up.
Bottas, 27, was set to remain with Williams into 2017, alongside Lance Stroll, but Nico Rosberg’s shock decision to retire as World Champion opened a vacancy at Mercedes.
Mercedes courted several drivers but eventually settled on Bottas, with Felipe Massa having confirmed that he will stay on at Williams for an additional season.
"It's very exciting times for me," he said. "I think it's going to take a while to understand that this is really happening. It's definitely another dream come true, to race in another team with such great history – especially in the recent years, which have been so impressive.
"I'm really proud to become a part of that and grateful to everyone at Mercedes for trusting my skills and giving me this opportunity.
"I've had a really warm welcome so far. Of course, I have a lot more people to meet and new faces to remember. But initially everything has felt very good. I'm really impressed with the facilities and I'm looking forward to getting to know everyone better.
"My first experience with Mercedes power was in F3 back in 2009 and, of course, I know the Power Unit well from the last three years with Williams. But there are a lot of new things to learn with the car and also with how the team operates at the factory, in testing and at the races."
Bottas has previously spent the entirety of his Formula 1 career with Williams, having joined as its development driver in 2010.
Bottas went on to claim the GP3 title in 2011 and spent a season conducting practice runs in 2012, prior to graduating to a race seat the following year.
Williams endured a troublesome campaign as it grappled with the Coanda exhaust layout, but Bottas impressed against Pastor Maldonado, taking third on the grid during a damp qualifying session at Montréal, before logging eighth in the United States, the team’s highest result of the year.
Bottas was joined by Massa for 2014 and Williams propelled itself up the grid courtesy of a switch to Mercedes power units and an aerodynamically efficient FW36.
Bottas claimed his first podium in Austria and followed it up with another four rostrum finishes, including successive second places in Britain and Germany, placing fourth in the standings.
Williams remained the third-best team in 2015 but a more static pecking order meant Bottas was only able to take two podiums, in Canada and Mexico, finishing fifth overall.
Williams began 2016 harbouring ambitions of challenging for second in the standings but slumped to fifth, its predicament exacerbated by mid-season upgrades failing to deliver expected progress.
Bottas climbed onto the podium just once, in Canada, and slipped to eighth in the standings.
The Finn will partner three-time World Champion Hamilton at Mercedes, the Briton having relinquished his crown to Rosberg after missing out in the Abu Dhabi finale.