Zhoushan, formerly romanized as Chusan, is an urbanized archipelago with the administrative status of a prefecture-level city in the eastern Chinese province of Zhejiang. It consists of an archipelago of islands at the southern mouth of Hangzhou Bay, off Ningbo. The prefecture's city proper is Dinghai on Zhoushan Island, now administered as the prefecture's Dinghai District. During the 2020 census, Zhoushan Prefecture's population was 1,157,817, out of whom 882,932 lived in the built-up area made of two urban districts of Dinghai and Putuo.
On 8 July 2011 the central government approved Zhoushan as Zhoushan Archipelago New Area, a state-level new area.