The youngster takes the place of Ferrari-backed Italian driver Antonio Giovinazzi, while Finnish veteran Kimi Raikkonen is retiring.
FIA F2 frontrunner Zhou has been favourite to land the job for some months, helped by the rumoured $30 million sponsorship support he brings.
Formula 1 chief executive Stefano Domenicali said the signing was “fantastic for the sport and millions of passionate Chinese fans that now have a home hero to cheer all year long.”
The 22-year-old replaces Antonio Giovinazzi, who has been dropped after three seasons with the team but may retain a reserve role via his links with Ferrari.
His leaving means the team does not have an Italian driver.
Zhou has been with the Alpine Team since 2019.
Guanyu Zhou becomes China’s first-ever F1 driver as he completes the 2022 grid by signing for Alfa Romeo; a 22-year-old F2 driver will partner Valtteri Bottas, joining from Mercedes; Antonio Giovinazzi leaving Alfa after three years with the team.
Zhou will make his on-track debut with Alfa in the Abu Dhabi test in December.
The Swiss team have been given a free hand regarding driver choice of the 2022 season, as
Kimi Raikkonen’s record-breaking F1 career-ending, meaning Alfa Romeo, has an all-new line-up for the new season.
The 41-year-old former world champion, Kimi Raikkonen, said, ‘It was not an easy decision, but after this season, it is time for new things,’ having had a career spanning 20 years, 21 race wins and 103 podiums.