Russell has revealed he and Williams team-mate Nicholas Latifi were only informed of the decision on Thursday morning, just hours ahead of the official announcement.
Russell said: "Claire broke the news to us this morning. Obviously, It is a sad day for us.
"For me personally, Frank and Claire gave me my opportunity in Formula 1, something I am very thankful and grateful for and obviously, having the opportunity to drive for such an amazing and prestigious team for the two years I have been here so far.
"It's sad to see the Williams family step aside but the history of Williams will still remain under Williams Racing and we will continue to fight and represent the family name."
Latifi admitted he was "shocked" by the timing of the revelation but remained adamant the "culture" of Williams will not leave with the family.
"From my side, I was definitely a bit shocked to hear the news this morning," he said.
"I think when the news broke that the team was sold, it was definitely something in the back of my mind that was maybe I could have anticipated but I just wasn't expecting it so soon.
"I think the whole sale of the team, in general, happened much quicker than everyone thought.
"For me, I have done my first full season in Formula 1 but I have been with the team and in the team environment and part of the Williams family these last years and for sure it is very special that I was given my first opportunity to come into Formula 1.
"I hope that I have a very long career and I think it is always going to be special that where I started out was here with Williams.
"They have given many drivers their first opportunity and not just drivers, the team members and the culture and atmosphere and environment that has been cultivated over the years is going to remain the same.
"It won't go just because Claire and the family are stepping aside. I am grateful for them to have given me this opportunity."
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