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. The largest island of the province used to be Hainan Island, which was carved out of Guangdong to form a separate province in 1988.
The population of the island is 16,320.
It is known in history for having been the place of death of St. Francis Xavier.
Administratively, Chuandao (川岛镇) is one of the 16 towns of Taishan county-level city.
Shangchuan Island was one of the first bases established by the Portuguese off the China coast, during the 16th century. They abandoned this base after the Chinese government gave consent for a permanent and official Portuguese trade base at Macau in 1557.
The Spanish (Navarre) Jesuit missionary St. Francis Xavier died on the island on December 2, 1552, as he was waiting for a ship to take him to mainland China.
The island has been isolated from the mainland since the last ice age. It is located near Xiachuan Island, which lies west of Shangchuan. The two islands, together with smaller islet, form Chuanshan Archipelago.