The Palni Hills are a range of mountains in Tamil Nadu. The hills are actually an eastward extension of the Western Ghats, which are located in the west coast of India. Sprawling over an area of 2068 square kilometers, on the west of Palni Hills lie the Anamalai range and in the east it extends in the plains of Tamil Nadu. The highest part of the range is in the southwest where the elevation ranges1, 800-2,500 meters above mean sea level. The eastern part of the range has an elevation of 1500-1000 meters above mean sea level.

The Palni Hills is surrounded by the Kambam Valley on the south, which is drained by the Vaigai River and its upper tributaries and the Kongu Nadu in the north. The northern slopes of the Palni Hills is drained by the tributaries of the Cauvery River namely, Shanmukha River, Nanganji River, and Kodavanar River. The range covers a major portion in the Dindigul district except in the west where it forms the border between Dindigul district and Theni district.

The vegetation of the hills varies from elevation to elevation. The lower elevations of the Palni Hills between 250 to 1000 meters have the South Western Ghats moist deciduous forests ecoregion. Above one thousand meters there is the evergreen South Western Ghats montane rain forests. Above one thousand meters the vegetation changes to shoal grassland mosaic comprising of frost tolerant montane grasslands.

There is a temple on the hill dedicated to Lord Karthikeyan or Murugan, one of the revered gods in Tamil Nadu. The famous hill station Kodaikanal lies in the northwestern part of the range.