Wiseman will immediately begin his rehab, and his status will be updated in September.
The 20-year-old tore the meniscus in his right knee Saturday against the Houston Rockets. He suffered the injury in the second quarter when he landed awkwardly after having his dunk attempt blocked.
The rookie averaged 11.5 points and 5.8 rebounds in 39 games this year, making 27 starts. He also missed three weeks in February with a sprained wrist.
Golden State selected Wiseman second overall in last year's draft. He's the second top-three pick in 2020 to be ruled out long term this season; Charlotte Hornets guard LaMelo Ball, who was taken third, has yet to play since suffering a wrist fracture in late March. However, a return for Ball this season hasn't been ruled out entirely.