Koh Seh (Khmer: កោះសេះ, also romanized as Kaoh Seh and its former French name Ile a l'eau) is a Cambodian island located in the Gulf of Thailand, inside Ream National Park, Sihanoukville province. It lies 1.5 km (1 mi) south of Koh Thmei and around 9 km (6 mi) south of the main-land of Sihanoukville's Ream commune. A 4.3 km (3 mi) wide sound separates it from Phu Quoc. "Koh Seh" means Horse Island. Less than 400 meters south-west of Koh Seh lies the tiny islet of Koh Ky.
