The Stevenage-born driver, who spent 14 years at McLaren, has expressed his 'excitement' in signing a three-year deal and replacing Michael Schumacher in the German-based team.
"It is now time for me to take on a fresh challenge and I am very excited to begin a new chapter racing for Mercedes," said Hamilton.
"Mercedes-Benz has such an incredible heritage in motorsport, along with a passion for winning which I share. 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."