Guanyu Zhou is replacing Antonio Giovinazzi for 2022 and will partner Valtteri Bottas at Alfa Romeo, completing the grid for Formula 1's new era.
Zhou, a highly-rated prospect in Formula 2, will become the first full-time Chinese F1 driver and also ensures Alfa, currently ninth in the championship, have an all-new driver line-up next year.
Bottas is the team's big signing for 2022 from Mercedes.
Just before confirming Zhou, the Italian outfit thanked Giovinazzi for his "extraordinary contribution" over three years, but he did not do enough to prevent the team opting for the 22-year-old "trailblazer", who has tested for Alpine as a reserve driver and will be the only rookie on next year's grid.
"To be the first ever Chinese driver in Formula 1 is a breakthrough for Chinese motorsport history," said Zhou, who is second in this year's F2 championship.
"I dreamt from a young age of climbing as high as I can in a sport that I am passionate about and now the dream has come true."
Team boss Frederic Vasseur added: "He is a very talented driver, as his results in F2 have shown, and we are looking forward to helping his talent flourish even more in Formula 1."