The island was probably first inhabited about 15 centuries ago, settled by fishermen from the Malay Peninsula and Southern China. It appears on Chinese maps dating back to 1687, under the name Pulo Cornam. The name Samui is mysterious in itself. Perhaps it is an extension of the name of one of the native trees, mui, or it is a corruption of the Chinese word "Saboey", meaning "safe haven".
Until the late 20th century, Samui was an isolated self-sufficient community, having little connection with the mainland of Thailand. The island was even without roads until the early 1970s, and the 15km journey from one side of the island to the other involved a whole-day trek through the mountainous central jungles.
Samui is located in the Gulf of Thailand, about 35km northeast of Surat Thani town (9°N, 100°E). It is surrounded by about sixty other islands, most of which comprise the Ang Thong National Marine Park, but also include other tourist destinations Ko Pha Ngan, Ko Tao and Ko Nang Yuan.
Administratively, Ko Samui is an Amphoe (district) of Surat Thani Province. The district is subdivided into 7 subdistricts (tambon). Also the complete island is one municipality (thesaban tambon). The district covers the island, as well as the Ang Thong archipelago and some other small islands nearby.
Historically the island's economy has been based around subsistence agriculture and fishing, with coconuts as the main cash crop. From the 1980s onwards however, tourism has become an economic factor and is now the dominant industry. The construction of a stable, high-speed internet connection in recent years has also made the island a practicable location for IT-based enterprises, which are beginning to provide a certain degree of economic diversity. The island's climate and accessibility make it particularly attractive for international investors.