The red deer (Cervus elaphus) is one of the largest deer species. The red deer inhabits most of Europe, the Caucasus Mountains region, Asia Minor, parts of western Asia, and central Asia. It also inhabits the Atlas Mountains region between Morocco and Tunisia in northwestern Africa, being the only species of deer to inhabit Africa. Red deer have been introduced to other areas, including Australia, New Zealand and Argentina. In many parts of the world, the meat (venison) from red deer is used as a food source.

Red deer are ruminants, characterized by an even number of toes, and a four-chambered stomach. Genetic evidence indicates the red deer (Cervus elaphus) as traditionally defined is a species group rather than a single species, although it remains disputed as to exactly how many species the group includes. The slightly larger American elk or wapiti, native to North America and eastern parts of Asia, represents a distinct species besides red deer. The ancestor of all red deer, including wapiti, probably originated in central Asia and probably resembled sika deer.

Although at one time red deer were rare in some areas, they were never close to extinction. Reintroduction and conservation efforts, especially in the United Kingdom, have resulted in an increase of red deer populations, while other areas, such as North Africa, have continued to show a population decline.