The line-up was announced at a special press event in Milan, Italy on Saturday, where the team revealed further details of their new title sponsorship deal with Alfa Romeo, including a revised red and white livery concept for next season's auto and a new logo.
Sauber announced earlier this week it would be racing as "Alfa Romeo Sauber" in 2018, heralding the return of the Alfa Romeo name to F1 after more than 30 years.
Meanwhile, in terms of drivers, the Swiss team are retaining the services of Marcus Ericsson, but are replacing Pascal Wehrlein with the services of Charles Leclerc.
It's believed that Ferrari had been pressing for another of their development drivers, Antonio Giovinazzi, to take the race seat.
The white-and-red scheme, reflecting Alfa Romeo's colours, marks a move away from the predominantly blue livery which Sauber has run since 2015.
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Giovinazzi will be the reserve driver instead, taking part in Friday practice sessions. He was speaking in Milan at an event marking the launch of Sauber's new partnership with Alfa Romeo.
Marchionne warned, however, that the deal could end in 2021 should Ferrari leave Formula One at that point because of a disagreement over the direction of the sport under new owners Liberty Media.
"Now there is the additional benefit that when we sit down at the table to discuss the future of Formula One, we're playing two marques", he told reporters.
"It's an fantastic opportunity for me but also for the team", said Ericsson, whose financial support has always been linked to Rausing and the Tetra Laval packaging group.