Zhoushan Island in the context of "Chongming Island"

Zhoushan 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 the mainland city of 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 builtup (or metro) area consisting of two urban districts of Dinghai and Putuo.

On July 8, 2011, the central government approved Zhoushan as Zhoushan Archipelago New Area, a state-level new area.

Dinghai (simplified Chinese: 定海区; traditional Chinese: 定海區; pinyin: Dìnghǎi Qū) is a district of Zhoushan City made of 128 islands in Zhejiang province, China. The total area is 1,444 square kilometres. The land area is 568.8 square kilometres, the sea area is 875.2 square kilometres, and the coastline is more than 400 kilometres. It is based on the larger northwestern half of Zhoushan Island, where it borders Putuo in the east. The district boundary meets that of Daishan County out at sea to the north of the island. Its southwestern boundary intersects the border of Ningbo, also entirely at sea.

The district, which was formed in January 1987 when it was upgraded from county status, has a population of 399,382 as of 2019.