Charles Leclerc will make his Formula 1 debut next season after being confirmed alongside Marcus Ericsson in Sauber's line-up.
Ferrari-backed Leclerc, 20 and from Monaco, had been expected to get the Sauber drive after a dominant season in the official feeder series.
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.
Saturday's event showed off a new red and white livery, with Alfa Romeo branding prominent on the engine cover, and a redesigned logo.
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Florida State (5-6) faces Louisiana-Monroe on Saturday and needs a win to be bowl eligible for a 36th consecutive season. Information from ESPN's Mark Schlabach and Sam Khan Jr. and The Associated Press was used in this report.
Giovinazzi will stay as the team's back-up driver and it remains to be seen if Wehrlein moves to Williams - the only remaining team with a vacancy.
"The motor we use will be the same one Ferrari use", Marchionne said. 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. "First and foremost, I would like to thank Ferrari for their support". Next year's auto will also be equipped with Ferrari power units. The team parted company with former team boss Monisha Kaltenborn, who was replaced by Frederic Vasseur, before abandoning a Honda engine deal which had been agreed earlier in the season.