(CNN) -- Nico Rosberg is the first signing for the new Mercedes Grand Prix team after their takeover of all-conquering Brawn GP.
The 24-year-old German, who is the son of former F1 world champion Keke Rosberg, switches from Williams where he has spent the last four seasons.
"I am really happy to be a part of the Silver Arrows relaunch in 2010 as a driver for Mercedes," Rosbeg told the team's official Web site www.brawngp.com.
Rosberg fills one of the two slots in the team caused by the departures of world champion Jenson Button and Brazilian Rubens Barrichello.
Speculation has been mounting that seven-time world champion Michael Schumacher will be the other driver but team principal Ross Brawn has ruled it out.
He told the Web site of the Bild newspaper in Germany that the story was a media invention.
"There's nothing to the rumors," he was quoted.
"The media have just let their imagination run wild. If Michael had come back for Ferrari -- it would only have been temporary. He doesn't have any ambitions of mounting a comeback."
Brawn, who remains in charge after selling most of his controlling interest in the team to Mercedes, believes Rosberg is the perfect signing.
"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."
If the Schumacher rumors do not come to fruition, another German, Nick Heidfeld remains the most likely driver to partner Rosberg next season.
Heidfeld is without a drive after his BMW-Sauber team was dissolved at the end of the season.
Benson and Barrichello powered Brawn GP to the constructor's title in their first season, with the new champion winning six of the opening seven races.
Button jumped ship to McLaren to join 2008 world champion Lewis Hamilton, with veteran Barrichello going to Williams.
Schumacher has a long-standing relationship with technical guru Brawn dating back to his Ferrari days and was slated for a return to F1 for the stricken Felipe Massa before a neck injury ended his hopes.