Vihorlat Mountains (Slovak: Vihorlatské vrchy; Ukrainian: Вигорлат, Vyhorliat) or colloquially Vihorlat is a volcanic mountain range in eastern Slovakia and western Ukraine. A part of the range is listed as a World Heritage Site.
The Slovak part is 55 km long, up to 11 km broad and from 400 to 1,076 m high. It belongs to the Vihorlat-Gutin Area group of the Inner Eastern Carpathian Mountains. The middle part of the mountains is protected by the Vihorlat Protected Landscape Area.
Vihorlat is bordered by the Eastern Slovak Lowland (Východoslovenská nížina) in the south and the west. The Beskidian Piedmont (Beskydské predhorie) separates Vihorlat from the Bukovské vrchy mountains and Laborecká vrchovina highlands in the north. The highest peak is Vihorlat at 1,076 m AMSL. The largest lake in the mountain range is Morské oko, which is situated at 618 m AMSL.