Mercedes Grand Prix have announced Nico Rosberg as their new driver in their first signing since taking over the Brawn GP team.
The 24-year-old German ended his four-year association with Williams to team up with the newly-branded team which last week saw world champion Jenson Button move to McLaren.
Rosberg said: "I am really happy to be a part of the Silver Arrows relaunch in 2010 as a driver for Mercedes."
Rosberg added: "No other brand in Formula One can look back on such a long and successful tradition in motor racing. I am very proud that I will now drive for the new Mercedes team and work with Ross Brawn.
"I am more motivated than ever and can hardly wait to start testing with the new Silver Arrow and for the first race of the new season at Bahrain in March."
Rosberg has been singled out as the perfect signing for the team by principal Ross Brawn, who guided the team named after him to the drivers' and constructors' titles in their debut season before selling a controlling interest to Mercedes.
Brawn said: "We are delighted to welcome Nico to our Mercedes team and are very much looking forward to working with him.
"Nico is a great talent and, with four years of experience in Formula 1, is a driver who will be able to make a valuable contribution to our team right from the outset.
"I had the pleasure of working with his father Keke during his Formula One career and it is great to see Nico following in his footsteps.
"2009 was Nico's best season in Formula One to date and we look forward to seeing his development continue with us at Mercedes next year."