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, with Kimi Raikkonen's record-breaking F1 career heading into its final three races.
Just before confirming Zhou, the Swiss-based 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.
"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."
Alfa opt for youth to complete 2022 grid
Giovinazzi joined Alfa Romeo back in 2019 as a Ferrari-backed driver and has shown improvements, without the obvious stardom that Charles Leclerc had before him with the team.
Giovinazzi, 27, has outqualified Raikkonen this year but has still scored fewer points than the veteran Finn and, in his 57 races in F1, has finished in the top-10 only eight times with a best of fifth at the 2019 Brazilian GP.
His exit leaves F1 without an Italian driver.
Alfa's signing of Zhou, meanwhile, is another F1 show of faith in a talented young crop of drivers.
Zhou has driven in the F2 feeder series for the last three seasons, finishing 7th in 2019, sixth in 2020 while he is currently second, behind fellow Alpine junior Oscar Piastri, in the 2021 standings.
He has won four races in that time, three of which coming this year.
His arrival also completes the grid with all 10 teams having confirmed their two-driver line-up for a season which will welcome brand new rules and all-new cars.
Alfa are one of only three teams changing their line-ups. Mercedes have replaced Bottas with George Russell, while Williams have drafted in Alex Albon to fill that spot.
There are three races remaining in the 2021 season, starting with the debut Qatar GP this weekend, live on Sky Sports F1.