Antonio Giovinazzi, another Ferrari product, will be the team's third driver.
Sauber, meanwhile, had Marcus Ericsson angling for a seat despite not scoring any points in either of the last two seasons, relying heavily on his links to the team's owners.
Even before he put his teenage years behind him back in October, he had always been the favorite to get this ride, and now it's official.
Leclerc and Ericsson unveiled the team's livery, pulling back covers to reveal a red and white showcar, with a large Alfa Romeo logo on the engine cover.
ARESE, Italy, Dec 2 (Reuters) - Formula Two champion Charles Leclerc will move up to Formula One with Alfa Romeo-backed Sauber next season while Marcus Ericcson stays in the lineup despite the Swede failing to score a point in 2017. They have linked up with Alfa Romeo, who will become their title sponsor, for the 2018 season in a deal that marks a return to F1 for the Italian firm after a 30-year absence.
Super "Frost" moon this weekend
Nearby perigee full Moons appear about 14% bigger and 30% brighter than full Moons that occur near apogee in the Moon's orbit. Stargazers will get a chance to witness the first and only supermoon of this year Sunday night.
Ferrari's late founder Enzo also started out racing and managing a team for Alfa Romeo, before setting up on his own in the late 1930s.
Formula One chairman Chase Carey and former Ferrari boss Jean Todt, president of the governing FIA, both attended the presentation.
"It's a very important agreement for F1", Todt said.
Besides the one remaining seat at Williams alongside Lance Stroll, Sauber was still yet to confirm either of its 2018 drivers, with three candidates being in contention.
"We've got a long way to go to catch up and succeed", Vasseur said. The most important of these upgrades Sauber from running a Ferrari engine that is a year old to a current power unit instead.
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