Deogyusan (Korean: 덕유산), formerly spelled Togyusan, is a mountain in South Korea.

Deogyusan stands on the border of North Jeolla Province and South Gyeongsang Province, covering portions of Muju and Jangsu Counties in Jeollabuk-do and Geochang and Hamyang Counties in Gyeongsangnam-do.

It is composed of numerous ridges which rise to various local peaks; the highest (by which the mountain's elevation is measured) is Hyangjeokbong.

The attractions of the park include the Chiryeon Waterfall and Cheoksan mountain fortress.

An Amur Leopard was shot on Deogyusan in 1960, a few years before the species disappeared from South Korea.