Shangchuan Island (Chinese: 上川岛; pinyin: Shàngchuāndǎo, also known as "Schangschwan", "Sancian", "Sanchão", "Chang-Chuang", "St. John's Island" or "St John Island") is the main island of Chuanshan Archipelago on the southern coast of Guangdong, China.

Administratively, it is a part of Chuandao (川岛镇), Taishan. Located 14 kilometers (8.7 mi) from the mainland, it became the largest island in Guangdong after Hainan Island (the largest island in the country) was carved out of the province in 1988.

The area of the island is 139.87 square kilometers (54.00 sq mi), and has a population of 16,320.

It is known for having been the place of death of St. Francis Xavier. Nowadays, it is a tourist site in Guangdong.

The island was called Shangchuan Shan (上川山) in the Ming dynasty, as recorded in the Records of the Unity of the Great Ming (大明一統志) published in 1461.

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 (Navarrese) Jesuit missionary St. Francis Xavier died on the island on December 3, 1552, as he was waiting for a ship to take him to mainland China. There is a small chapel that commemorates his death place, designed by Achille-Antoine Hermitte and completed in 1869.

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 islets, form Chuanshan Archipelago.