Mudumalai National Park is a national park in the Nilgiri Mountains in Tamil Nadu in southern India. It covers 321 km2 (124 sq mi) at an elevation range of 850–1,250 m (2,790–4,100 ft) in the Nilgiri District and shares boundaries with the states of Karnataka and Kerala. A part of this area has been protected since 1940. The national park has been part of Nilgiri Biosphere Reserve since 1986 and was declared a tiger reserve together with a buffer zone of 367.59 km2 (141.93 sq mi) in 2007. It receives an annual rainfall of about 1,420 mm (56 in) and harbours tropical and subtropical moist broadleaf forests with 498 plant species, at least 266 bird species, 18 carnivore and 10 herbivore species. It is drained by the Moyar River and several tributaries, which harbour 38 fish species.

The Nilgiri Mountains form part of the Western Ghats in northwestern Tamil Nadu, Southern Karnataka, and eastern Kerala in India. They are located at the trijunction of three states and connect the Western Ghats with the Eastern Ghats. At least 24 of the Nilgiri Mountains' peaks are above 2,000 metres (6,600 ft), the highest peak being Doddabetta, at 2,637 metres (8,652 ft).