During a press conference held at Alfa Romeo's museum on Saturday, Leclerc and Ericsson took the wraps off the squad's proposed 2018 livery, which was presented on one of the team's showcars.
"I am very happy to be entering Formula One in 2018", said the rook.
F2 champion LeClerc had always been expected to make the jump to the pinnacle of motorsport.
The Swiss Formula One outfit Alfa Romeo Sauber have confirmed that Sweden's Marcus Ericsson and young Frenchman Charles Leclerc will compete for the world title in their rebranded auto in 2018.
The Alfa Romeo name last appeared in F1 in 1985, although its biggest achievements came during the series' first two years, when Giuseppe "Nino" Farina and Juan Manuel Fangio won the 1950 and 1951 titles, respectively.
Formula One chairman Chase Carey and former Ferrari boss Jean Todt, president of the governing FIA, both attended the presentation.
Despite scoring all five of the team's points for Sauber this season, Wehrlein now only has Williams as an option in F1 for 2018, with the Mercedes youngster facing a potential return to DTM. "But Mr. Marchionne is not the most patient so we have to speed things up".
The multi-year deal includes strategic, commercial and technological cooperation, enhancing an arrangement that already included use of the latest specification Ferrari engine.