Theni Allinagaram is a city and a municipality in Theni district in the Indian state of Tamil Nadu.

As of 2001^[update] India census, Theni Allinagaram had a population of 85,424. Males constitute 51% of the population and females 49%. Theni Allinagaram has an average literacy rate of 74%, higher than the national average of 59.5%: male literacy is 80%, and female literacy is 67%. In Theni Allinagaram, 11% of the population is under 6 years of age.

Coordinates: 10°00′43″N 77°28′43″E / 10.01194°N 77.47861°E / 10.01194; 77.47861

Theni pronunciation (help·info) is a town in the Western Tamil Nadu state of South India. It is the headquarters of Theni District. It is known for the large-scale trading of Cardamom, Cotton, Grapes, Chilli and Textiles. It hosts the second largest weekly market in Tamil Nadu and the fourth largest in South India. It is well-connected by rail and road to Madurai and by road to all the important cities in Tamil Nadu. The nearest airport is at Madurai.

Theni district is surrounded by the Western Ghats. The main occupation of people of Theni is agriculture. The Vaigai River flows through this district. Other important rivers include the Mullaiperiyar, Suruliyaru, Varaganadi, Kottakkudiyaru, and Manjalaru rivers.

Theni has a historic background during the 19th century. There were many antagonists against British rule like Marutha Nayagam.

The famous Saneeswaran (God of Saturn) temple is located in the Kucchanur Village.It is a Suyambhu statue and Pathirakaliyamman Temple, Pathirakalipuram.

Theni district is rich in flora and fauna. Many dams have been constructed on the rivers, including Vaigai Dam, Sothupparai Dam, Manjalaru Dam, and Meghamalai Dam. Several famous waterfalls are here: Suruli Falls, Kumbakarai Falls and Meghamalai Falls. Theni is surrounded by many tourist attractions like Kodaikannal, Thekkady, Meghamalai, Munnar, Kumbakkarai, Sothuppaarai and Vaigai dam. Because Theni's scenic environment, it is one of the most favoured shooting spots of the Tamil film industry. Thekkady wildlife sanctuary is a nearby attraction which lays in the border between Kerala and Tamil Nadu. There is a temple where Kannaki (historic character) was believed to be turned statue.