Valtteri Bottas will stay at Mercedes as Lewis Hamilton's team-mate in 2019.
Mercedes have signed the 28-year-old Finn to a one-year contract extension, with an option to keep him for 2020.
Bottas convinced Mercedes to retain him after some strong performances in the first half of this year.
Team boss Toto Wolff said: "Valtteri's performances have been excellent. If not for our mistakes and his bad luck, he could be leading the drivers' championship."
Bottas impressed with his drives in China, Azerbaijan and Austria.
He was leading in Shanghai before a mid-race safety car changed the complexion of the race and Red Bull's Daniel Ricciardo was able to win after a switch to fresh tyres, which was not an option for Bottas.
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In Azerbaijan, Bottas was leading with four laps to go when he suffered a high-speed puncture after running over debris.
And at the Red Bull Ring, Bottas was running a close second to Hamilton when his car suffered a hydraulic leak.
News of Mercedes' decision to keep Bottas comes a day after the team confirmed they had signed Hamilton for another two seasons.
Bottas' team work and the lack of tension between the two drivers have been key factors in Mercedes' desire to keep him.
Wolff added: "When we took the decision in favour of Valtteri for 2019, it wasn't just about his undoubted speed and work ethic, but also a question of character.
"His relationship with the team, including Lewis, is open and trusting, without any politics at all. Those are the ingredients you need when you're fighting strong rivals in both championships and they mirror the values inside the team."
Bottas, who joined Mercedes before the 2017 season after the shock retirement of world champion Nico Rosberg, said: "This year, with a full winter of preparation, I have been able to make a good step forward - and I believe that there is still more to come.
"We have not been so lucky in the races this year but the team knows how I am performing, and this is a great sign of confidence in me and my driving.
"We have a big battle on our hands right now, so it's good to have the future clear for everybody - it means we can have a full focus on the championship fight.
"Obviously, my goal is to keep performing at a high level - and to make it a no-brainer for the team when it comes to deciding their plans for 2020 as well."