Hòn Sơn (officially Lại Sơn) is one of the larger inhabited islands in the Kiên Hải island group of Kiên Giang province, situated in the Gulf of Thailand between the mainland and Phú Quốc. Unlike many of the province's smaller outer islands, Hòn Sơn has enough elevation and size to support a varied landscape - steep forested hills, multiple beaches with different characters, and a fishing community spread across the island's main settlement.
The crossing from Rạch Giá takes about 1.5 hours and the seas are calmer than the Phú Quý route - easier on those prone to seasickness. Accommodation ranges from basic guesthouses and homestays to small resorts, bungalows, and beachfront options - more developed than the remote outer islands but nothing close to Phú Quốc's scale. The water is clear enough for casual snorkeling in the dry season.