Satun (Thai: สตูล, pronounced [sā.tūːn]) is one of the southern provinces (changwat) of Thailand. Neighboring provinces are (from north clockwise) Trang, Phatthalung, and Songkhla. To the south it borders Perlis of Malaysia. The name Satun is a Thai version of its original Malay name, Setul (santol, or wild mangosteen tree).
The province is on the Malay Peninsula, on the shore of the Andaman Sea. It is separated from Songkhla Province by the Nakhon Si Thammarat mountain range, and from Malaysia by the Sankalakhiri mountains. The Ko Tarutao and Ko Phetra marine national parks are part of the province. Close to the border with Malaysia is the Thale Ban National Park, a big freshwater swamp area.
Until 1813 Satun was a district of the Malay state of Kedah, then known as Setul Mambang Segara or Mukim Setul (Jawi: مقيم ستول) in Malay. After that date it was administered by a governor sent from Nakhon Si Thammarat. In 1897 Satun became part of Monthon Saiburi (now Kedah), which in 1909 was divided between British Empire and Siam as part of Anglo-Siamese Treaty of 1909. While most of Kedah was ceded to Britain, Satun was awarded to Siam because it had a relatively large Thai population. Satun was then incorporated into Monthon Phuket. The monthon system was ended in 1933, and Satun province became a first-level subdivision of Thailand.