Lewis Hamilton will be partnered by Valtteri Bottas for a second season after Mercedes confirmed the Finnish driver has been retained for next year.
Bottas, who replaced reigning world champion Nico Rosberg at Mercedes following his shock retirement, has won two races this year and heads into Sunday's Singapore Grand Prix third in the standings, 41 points adrift of championship leader Hamilton.
The 28-year-old Finn has agreed a one-year deal, which allows Mercedes to keep their options open with Daniel Ricciardo and Max Verstappen both contracted at Red Bull until the end of 2018.
Hamilton's deal with Mercedes also expires at the end of next year, but the Englishman is expected to sign a new long-term contract with the team.
Bottas, drafted in by Mercedes following Rosberg's decision to walk away from the sport only five days after he won the championship, has steadily impressed in his opening year. The cool-headed Finn also provides the team with much-needed stability following three years of bitter in-fighting between Hamilton and Rosberg.
Mercedes' non-executive chairman Niki Lauda revealed he had spoken to Sebastian Vettel about the German's future plans, but following the announcement of his new three-year extension with Ferrari last month, Bottas was always likely to be retained.
''We gave Valtteri a big challenge this year by joining the team at the eleventh hour, stepping up to the forefront of F1 and pairing with the sport's best driver as his team-mate,'' Mercedes boss Toto Wolff said on Wednesday. ''With that in mind, his results have been probably even more impressive.
''There have been ups and downs - more ups, fewer downs - and some great highlights like his two race wins in Russia and Austria. Overall, the balance of his performances and his upward trajectory made it a no-brainer for us to continue with him into 2018.
''For our team, the bonus factors are the respect and sportsmanship that have grown between our two drivers. The chemistry and dynamic between Valtteri and Lewis work and are what we need to take the fight to our competitors.''
Mercedes lead Ferrari in the constructors' championship by 62 points with only seven rounds remaining - and despite Singapore expected to suit the Italian team's car - are odds-on to secure a fourth consecutive title.
Bottas, who spent four seasons at Williams before his switch to Mercedes, secured his maiden pole position at the third round of the championship in Bahrain before landing his first win one race later in Russia. He also won the Austrian Grand Prix in June, but has been unable to keep pace with Hamilton in recent races.
''I am honoured and proud to continue to work with Mercedes-AMG Petronas Motorsport in 2018 and to remain part of the Mercedes family,'' Bottas said. ''Together, we continue to grow stronger day by day, and by keeping up our hard work I believe the sky is the limit.
''As a driver, I've been able to learn and grow massively, and we have already enjoyed some really good moments this season that I will never forget. Partnering Lewis has also been really good, and I'm enjoying the respect we have and the will to push this team forward together.
''However, there's always room for improvement and I still have not shown my full potential. I will continue to work hard on and off the track, to further improve my driving, get even better results and show that putting their trust in me was the right decision.''