The driver line-up was confirmed by Fiat Chrysler Automobiles CEO Sergio Marchionne during a launch event of the new Alfa Romeo Sauber partnership - announced earlier this week - in Milan.
Sauber will field Ferrari-backed Formula 2 champion Charles Leclerc alongside incumbent Marcus Ericsson, with the Scuderia's reserve driver Antonio Giovinazzi set to take up a third driver role.
It was a tough campaign for the Swiss-based marque, with Wehrlein taking only five points and Ericsson failing to score even one, but the hope is, with the new engine manufacturer on board, they might be more competitive next year.
The covers were then pulled off a showcar, revealing a red and white livery, with a large Alfa Romeo logo on the engine cover.
"It was a great experience to drive a few FP1 sessions and tyre tests for the Sauber F1 Team in 2017, during which the team welcomed me straight away", said Leclerc.
Formula One chairman Chase Carey and former Ferrari boss Jean Todt, president of the governing FIA, both attended the presentation.
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.
"It's an awesome 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.