The Bilgiri Hills, also known as the Biligirirangan Hills, are a range of hills in southern India. The Bilgiris run east-west, connecting to the Western Ghats range on the west end, and ending at the Cauvery River to the east. The ridgeline forms the boundary between Chamarajanagar District of Karnataka state to the north, and Erode District of Tamil Nadu to the south. Peaks include Kattari Betts at 1816 meters.

The Bilgiris are covered with dry broadleaf forest, part of the South Deccan Plateau dry deciduous forests ecoregion. The forests range from scrub forests at lower elevations, degraded by over-use, to the tall deciduous forests typical of the ecoregion, to stunted shola forests and montane grasslands at the highest elevations, which exceed 1800 meters. The forests form an important wildlife corridor between the Western Ghats and the Eastern Ghats, linking the largest populations of Asian Elephants and tigers in southern India. The forests of the Bilgiris are part of the Sathyamangalam Territorial Forest Division. The Bilgiri Rangaswamy Temple lies in Chamrajangar district, on the north slope of the Bilgiris. A wildlife sanctuary of 322.4 sq km was created around the temple on 27 June 1974, and enlarged to 539.52 sq km on 14 January 1987. Coffee and teak plantations cover much of the lower slopes.