Zhou is currently second in the F2® championship with three wins this season and two rounds still to go next month. He will replace Antonio Giovinazzi at Alfa.
He was part of the Ferrari driver academy between 2014 and 2018, before joining Renault in 2019 as a test driver.
Zhou will reportedly bring with him a sizeable financial package to Alfa Romeo.
"The financial side can't be hidden," team principal Frederic Vasseur said to BBC Sport, while also pointing to the success that his new driver has had in F2, with victories in Bahrain and Silverstone this year.
"I don't know if, in the end, he will be a champion or not in F2. But this won't change the potential that he is a frontrunner against some other very experienced guys.
"He also has the advantage that he was able to do some test days this season in F1, so he is not with zero mileage."
Zhou expressed his excitement about joining the team, telling the Alfa Romeo Racing website: "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.
"It is a privilege for me to start my Formula 1 racing career with an iconic team, a team that has introduced so much young talent into Formula 1 in the past. Now the dream is reality. I feel well-prepared for the immense challenge of Formula 1, the pinnacle of my sport, alongside a proven, world-class talent in Valtteri Bottas.
"Next year the target will be to learn as much as possible and as quickly as possible."
On becoming the first F1 driver from China, Zhou added: "To be the first-ever Chinese driver in Formula 1 is a breakthrough for Chinese motorsport history. I know a lot of hopes will be resting on me and, as ever, I will take this as motivation to become better and achieve more."