Zhoushan Archipelago (jō-shän), NE Zhejiang prov., China, in the East China Sea, at the entrance to Hangzhou Bay. It includes the main island of Zhoushan and about 100 lesser islands; Dinghai on Zhoushan is the major population center. The archipelago forms the richest fishing grounds off the China coast. The island of Putuo was a sacred center of Buddhism, with many ancient temples and monasteries. The name sometimes appears as Chou-shan Archipelago.