Valtteri Bottas will race with Alfa Romeo Racing in 2022 as widely anticipated, having agreed a multi-year deal with the Swiss outfit.
The news will pave the way for Mercedes to officially announce George Russell as Lewis Hamilton's new teammate next season.
"A new chapter in my racing career is opening: I’m excited to join Alfa Romeo Racing ORLEN for 2022 and beyond for what is going to be a new challenge with an iconic manufacturer," said Bottas.
"Alfa Romeo is a brand that needs no introduction, they have written some great pages of Formula One history and it’s going to be an honour to represent this marque.
"The potential of the setup in Hinwil is clear and I am relishing the opportunity to help lead the team forward up the grid, especially with the new regulations in 2022 giving the team a chance to make a leap in performance.
"I’m grateful for the trust the team has put in me and I cannot wait to repay their faith: I’m as hungry as ever to race for results and, when the time comes, for wins.
"I know Fred [Vasseur] well and I am looking forward to getting to know the rest of the team I am going to work with, building relationships as strong as the ones I have at Mercedes.
"I am proud of what I have achieved in Brackley and I am fully focused on finishing the job as we fight for another world championship, but I am also looking forward to the new challenges that await me next year."
Bottas is in the process of completing his fifth season with Mercedes, having won all of his nine career wins in Formula 1 with the Brackley squad which he joined in 2017 following Nico Rosberg's decision to retire from the sport.
The 32-year-old has been an important team player for Mercedes over the years, playing a significant part in the German manufacturer's four Constructors' titles achieved since 2017.
But the Finn has struggled for form throughout the current season, failing to deliver a race win while teammate Lewis Hamilton has put four victories under his belt so far this year.
Bottas' performance level relative to Hamilton coupled with George Russell's stock trending consistently higher gradually put the Finn at a disadvantage to the Briton who will fill his seat at Mercedes from 2022.
Hamilton recently praised Bottas tenure alongside him at Mercedes, the pair forming a trouble-free, harmonious tandem that contrasts with the tense and antagonistic relationship that prevailed previously between Hamilton and Rosberg.
"He is a decent human being and I think that’s at the core of why I have the respect I have with him, and on top of that he’s a fierce competitor," said the seven-time world champion.
"He never gives up, he just keeps pushing. He’s helped me deliver these championships with the team. I couldn’t have done it without him."
Bottas' new venture with Alfa Romeo will open a third chapter in his F1 career which started with Williams in 2013.
Mercedes team boss Toto Wolff paid tribute to the Finn's contribution to the German manufacturer's succes in F1 over the past five years.
"This hasn't been an easy process or a straightforward decision for us," said Wolff. "Valtteri has done a fantastic job over the past five seasons and he has made an essential contribution to our success and to our growth.
"Together with Lewis, he has built a benchmark partnership between two team-mates in the sport, and that has been a valuable weapon in our championship battles and pushed us to achieve unprecedented success.
"He would absolutely have deserved to stay with the team, and I am pleased that he has been able to choose an exciting challenge with Alfa next year to continue his career at the top level of the sport; when the time comes, he will leave us with huge goodwill from every single member of the team, and he will forever be part of the Mercedes family."
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