Lewis Hamilton will join Mercedes from next season on a three-year contract.
The decision to leave McLaren after a 14-year association with the team has been described by one source close to Hamilton as "the toughest of his career".
In a statement Hamilton said: "It is now time for me to take on a fresh challenge and I am very excited to begin a new chapter racing for the Mercedes Formula One Team. Mercedes-Benz has such an incredible heritage in motorsport, along with a passion for winning, which I share."
He added: "Together, we can grow and rise to this new challenge. I believe that I can help steer the Silver Arrows to the top and achieve our joint ambitions of winning the world championships."
More top news
Cloudy skies for many this Bank Holiday Sunday.
The brother of British holidaymaker Steven Cook who vanished in Crete 10 years ago has his family are "sure he's alive".
Neurologist and Author Dr. Oliver Sacks CBE who wrote popular case histories like “The Man Who Mistook His Wife for a Hat” has died aged 82.