The young Brit has dazzled in the junior divisions of the motorsport world in the last few seasons, and working under the Mercedes umbrella.
Russell won the GP3 title in 2017, before strolling to the F2 series trophy in 2018, following Charles Leclerc as the only men to have done the double.
Like Leclerc, Russell will move into F1 with the worst team from the season before, but the Monegasque driver did help Sauber into the midfield fight throughout the 2018 season.
Russell will not attempt to do the same with Williams, alongside experienced returnee Robert Kubica.
“I’ve come off the back of two amazing years and I’m ready for the challenge,” Russell said.
“Obviously I’m a rookie, I’m not going to go out there and do anything stupid. But I feel like this is my time and I’m ready to do the business.
“It’s a huge step up, not only in the speed aspect, from Formula 2 to Formula 1. There’s so much extra coming with it. You’re in the eyes of millions of viewers.
“I’ve gone from working with 30 team members in Formula 2 to 750 with Williams. There’s much more pressure on the driver’s shoulders than just driving the car.”
Russell should be ready for his first race weekend in F1 in March, having worked at Mercedes for the last few years.
He has been able to get up close and personal with the best team on the grid, and be able to learn from Lewis Hamilton.
“I’ve been in a very fortunate position in the last two years, being part of Mercedes and having the opportunity to be in the debriefs and the meetings alongside Lewis,” he admitted.
“It’s very surreal to be honest. The past couple of years, since joining the Mercedes programme, have been a step-by-step process.
“It almost felt like a natural step to get this opportunity. This is everything I’ve dreamed of.”