Periyakulam (Tamil: பெரியகுளம்) is a town and a Municipality in Theni district in the South Indian state of Tamil Nadu.

Periyakulam (PKM) is located at 10°07′N 77°33′E / 10.12°N 77.55°E / 10.12; 77.55. It has an average elevation of 282 metres (925 feet). It is located at the foothills of the Western Ghats bordering the neighbouring state of Kerala. It is one of the most fertile places in the state of Tamil Nadu. Agriculture is the primary occupation for the population here. It is also known as the "Mango City", as a major supply of mangoes from this city goes into Tamil Nadu's mango output. It stands on the bank of the 'Varaha' (in Hindu mythology, Lord Maha Vishnu's Boar incarnation) river. It is a fertile area that has an annual supply of surplus rainfall. The villages that are included are Kailasapatti, T.Kallipatti,Tamarai kulam, Vadugapatti and Melmangalam, villages that also stand on the banks of the Varaha River.

Periyakulam city has an area of 21 km2, within an Semi urban area now extending over as much as 55 km2 and it is located at 10°07′N 77°33′E / 10.12°N 77.55°E / 10.12; 77.55 It has an average elevation of 356 meters above mean sea level. The climate is dry and hot, with Northeast monsoon rains during October–December. Temperatures during summer reach a maximum of 40 and a minimum of 26.3 °C, though temperatures over 43 °C are not uncommon. Winter temperatures range between 29.6 and 18 °C. The average annual rainfall is about 135 cm.