|Area||24.74 km2 (9.55 sq mi)|
|Length||6.5 km (4.04 mi)|
|Width||6 km (3.7 mi)|
|Coastline||15.6 km (9.69 mi)|
Weizhou Island (simplified Chinese: ; traditional Chinese: ; pinyin: ) is a Chinese island in the Gulf of Tonkin. The largest island of Guangxi Zhuang Autonomous Region, Weizhou is west of Leizhou Peninsula, south of Beihai, and east of Vietnam. Administratively, it is part of Weizhou Town, Haicheng District of Beihai City.
Its north-south length is 6.5 kilometres (4.0 miles), east-west 6 kilometres (3.7 miles). The coast is 15.6 kilometres (9.7 miles), with 6 to 10 kilometres (3.7 to 6.2 miles) of sandy beach. Weizhou rises in the south, where Nanwan Port (; pinyin: nánw?n g?ng) is located. Coral reefs have been established around the island.
Weizhou Dao is China's youngest volcanic island. Its origin is probably from a mantle plume that rose 50-32 million years ago, as a result from the collision of the Indian and Eurasian plates. When the plume reached the asthenosphere, it helped to create the South China Sea by the plume's lateral flow. An evidence that the plume still exists is that a lot of basalt has since the Pliocene erupted in the South China Sea and its adjacent areas, for example the Yandunling () and Yantouling () volcanoes, Leiqiong () volcano group, Weizhou Island and Xieyang Island.
There have been four periods of volcanic activity on the site, the first one occurred in the early Pleistocene, when mainly ash began to erupt from the bottom of the sea.
The second time, between 9-225 million years ago, started with basaltic magma eruptions, and ended with pyroclastic eruptions. This was the time with the heaviest eruptions on Weizhou and Xieyang.
The third time began with large amounts of volcanic bombs and ended with basaltic magma, this was from 200,000 to 15,000 years ago.
The fourth time, from 10,000 to 7,100 years ago, a few intermittent eruptions happened, first mainly with volcanic bombs, and in the end volcanic ash.
From 1869 to 1879, the French built a Gothic-style 15 metre Catholic church in Shengtang Village (; pinyin: shèngtáng c?n), Weizhou. Weizhou Chengzai Church (?) was built in 1880, also by French Catholics.
Along with smaller Xieyang Island, Weizhou island is a nature reserve named Beihai Weizhoudao Volcano National Geopark to preserve its volcanic features and protect rich local ecosystem engulfing 147 species of migratory and non-migratory birds, including threatened species such as black-faced spoonbills.
Calm and shallow waters around the two islands have shown recoveries in recent years, resulting in support and attract varieties of marine life from coral reefs to megafaunas more increasingly appear such as sea turtles,whale sharks, endangered finless porpoises, several species of dolphins including nationally protected Chinese white dolphins, and Bryde's whales. Even a blue whale appeared in the waters in 2017.Hepu Dugong National Nature Reserve established in 1992 covers nearby areas and which is the only sanctuary for dugongs in China.