Basalt Island (Chinese: 火石洲; Sidney Lau: Foh2 Sek6 Jau1) is an island of Hong Kong and administratively part of the Sai Kung District. Together with Wang Chau and Bluff Island, it forms the Ung Kong (Chinese: 甕缸; Sidney Lau: Ung3 Gong1) Group and is part of Hong Kong Global Geopark.
On 21 December 1948, Basalt Island was the site of the first commercial airliner crash in Hong Kong, in which all 28 passengers, including five women, one child and seven crew, were killed. CNAC flight XT-104 from Shanghai to Hong Kong Kai Tak Airport was operated by a C-54 Skymaster. Fog over the island was the official cause of the crash.
Quentin Roosevelt II, the grandson of American president Theodore Roosevelt and then Senior Vice President of China National Aviation Corporation (CNAC), and Paul Yung, elder brother of Rong Yiren who was later to become Vice-President of the People's Republic of China, were among the casualties.
Debris remains near the site of the crash.
Basalt Island is located south of Town Island and Wang Chau, east of Bluff Island and north of the Ninepin Group. Its highest elevation is 174 m.