Sainz has signed a two-year agreement with the Scuderia and will partner Charles Leclerc from 2021, with Vettel due to leave the team at the end of the year, bringing to an end a six-season partnership.
A delighted Sainz said: "I am very happy that I will be driving for Scuderia Ferrari in 2021 and I'm excited about my future with the team.
"I still have an important year ahead with McLaren Racing and I’m really looking forward to going racing again with them this season.
Team principal Mattia Binotto said: "I’m pleased to announce that Carlos will join Scuderia Ferrari as from the 2021 championship.
"With five seasons already behind him, Carlos has proved to be very talented and has shown that he has the technical ability and the right attributes to make him an ideal fit with our family.
“We’ve embarked on a new cycle with the aim of getting back to the top in Formula 1.
"It will be a long journey, not without its difficulties, especially given the current financial and regulatory situation, which is undergoing a sudden change and will require this challenge to be tackled in a different way to the recent past.
"We believe that a driver pairing with the talent and personality of Charles and Carlos, the youngest in the past 50 years of the Scuderia, will be the best possible combination to help us reach the goals we have set ourselves."
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