Shangchuan Island (Chinese: 上川岛; pinyin: Shàngchuāndǎo) also written (Schangschwan, Sancian, Sanchão, Chang-Chuang or St. John's Island) is the main island of Chuanshan Archipelago on the southern coast of China. Its name originated from São João ("Saint John" in Portuguese). It is part of the Guangdong province, in the South China Sea. Located 14 km from the mainland, it is the largest island in the province.