Jungle usually refers to a dense forest in a hot climate, such as a tropical rainforest. About 6% of the Earth's land mass is classified as jungle. Jungles are vital to sustaining the ecosystems of the Earth as we know it. About 57% of all species live in jungle environments.

The word jungle originates from a Sanskrit word jangala, meaning "desert". In many languages of the Indian subcontinent, including Indian English, it is generally used to refer to any wild, untended or uncultivated land, including forest, scrub, or desert landscapes. Sometimes an urban environment can be called a jungle, as "concrete jungle".