World champion Nico Rosberg has announced he has retired from Formula 1 with immediate effect.
The 31-year-old German won his first world title on Sunday, beating Mercedes team-mate Lewis Hamilton by finishing second in the final race in Abu Dhabi.
"I have climbed my mountain, I am on the peak, so this feels right," Rosberg said.
Rosberg won nine of this season's 21 grands prix, beating three-time champion Hamilton by five points.
"For 25 years in racing, it has been my dream, my 'one thing', to become Formula 1 world champion," he added.
"Through the hard work, the pain, the sacrifices, this has been my target. And now I've made it."
The son of Finnish 1982 world champion Keke, Rosberg made his F1 debut for Williams at the Bahrain Grand Prix in 2006, finishing seventh.
And when asked if there was any chance of a return, Rosberg added: "No definitely not. End of story. Done."
Hamilton, who had beaten Rosberg to the title in the previous two seasons, said: "He has a family he wants to focus on, and F1 takes so much from you.
"It is definitely going to be strange and it will be sad to not have him in the team next year."
Mercedes team boss Toto Wolff said the news took him "completely by surprise".
"This is a brave decision by Nico and a testament to the strength of his character," he added.
"The clarity of his judgement meant I accepted his decision straight away when he told me.
"We now have to consider options and we will start to look at it on Monday."
Rosberg raced in 206 grands prix, winning 23 and finishing on the podium 57 times.
BBC Sport chief F1 writer Andrew Benson
Nico Rosberg's decision to announce his retirement from Formula 1 just five days after clinching his first world title is a major shock - but perhaps it should not be.
The German put everything into this season, as he explained in his statement on Friday. The pressure of those last few races was plain to see in Abu Dhabi on Sunday, in the way it peeled off him by degrees in the hours after the race.
While thinking about how hard winning that title was, doubtless his thoughts were also about what it would take to beat Lewis Hamilton to it again. He clearly felt that at the age of 31, with a young daughter, he was not prepared to make those sacrifices again.
All in all, it is a classy move from a classy man.