The 31-year-old announced his intentions on his official Facebook page, saying: "I have climbed my mountain, I am on the peak, so this feels right."
Rosberg clinched his first F1 drivers' title
at Sunday's season-ending Abu Dhabi Grand Prix where he finished second behind his Mercedes teammate Lewis Hamilton to win the championship by just five points
Social media reacted in disbelief to the German's announcement but found time for plenty of tributes and humor.
The now vacant seat at Mercedes got tongues wagging about who will partner Hamilton next season.
"Sebastian Vettel right now," tweeted @javiergrandio posting a picture of the four-time world champion on the phone with a caption reading "Hallo? Mercedes."
"Give the Mercedes seat to Vettel. That would be a mouthwatering clash with Hamilton" tweeted @teeman79.
At time of writing, Rosberg's official Facebook post has 12,000 comments, many of them, like David McMillan, paid tribute.
"This is massive news and certainly a surprise. Well, he won the world title and if he wanted to go out at the top, then congrats to him and all the very best for the future. All round top bloke deserves more credit."
Meanwhile, Ivan Nikolov pleaded with the German to reconsider:
"Take a rest and think again, it's the relieve of the pressure speaking right now Nico! Don't do it! You can achieve so much more! What are you going to be doing at home without challenges?"
The F1 community was also quick to pay tribute:
"Definitely a Great champion!!!! Big admiration @nico_rosberg #respect," wrote Force India driver Sergio Perez.
The McLaren team posted a picture of Rosberg with Felipe Massa and Jenson Button -- who both hung up their helmets after the Abu Dhabi Grand Prix -- noting "#F1 won't be the same without these three guys."
Toto Wolff was surprised by Rosberg's "unexpected" decision but the Mercedes team boss is already looking towards 2017:
"There's a free @mercedesAMGF1 cockpit for the season ahead..."
Which does beg the question: Who will fill Rosberg's shoes at the three-time world constructors' champions? Head to our Facebook page
to have your say.