Ko Samet or Ko Samed, is one of the Eastern Seaboard Islands of Thailand. It is located in the Gulf of Thailand off the coastline of the Thai province of Rayong, approximately 220 kilometres southeast of Bangkok. Ko Samet is part of the Phe District of the Amphoe Mueang Rayong, the capital district of Rayong province. Ko Samet is the largest and westernmost of a cluster of islands not far from the coast.
The island derives its name from the cajeput tree found throughout the island, as the Thai language word for cajeput is samet. In the past, this island has also been referred to by its colloquial name, Ko Kaew Phitsadan literally the "Magic Crystal Island".
Ko Samet is popular with foreign tourists and as a weekend getaway for residents of nearby Bangkok, most of the island (excluding the Na Dan area) belongs to the Khao Laem Ya - Mu Ko Samet National Park. In 1981, the Royal Forest Department declared the archipelago of Samet, along with nine other small islands, the headland of Khao Laem Ya, and the 11 kilometres Mae Rampeung Beach to be a National Park, and is thus Ko Samet is under the protection of the National Parks Division of the Thai Government.
Travel to and from Ko Samet is typically via the small local port at Ban Phé on the coast. Travellers from Bangkok frequently travel by bus, with departures to Ban Phé from Bangkok's Eastern Bus terminal, the Ekkamai bus station, and travel time from Bangkok to Ban Phé of approximately 3½ hours. Owing to the island's close proximity to the coast, just 7 kilometres offshore, boats travel casually from Ban Phé to Ko Samet in approximately 30 minutes.