Mahamaham, also known as Mahamagham or Mamangam, is a Hindu festival celebrated every 12 years in the Mahamaham tank located in the city of Kumbakonam in Tamil Nadu in the south of India. This 20-acre square tank surrounded by Shiva mandapams is believed by Tamil Hindus to be ancient, and the holy confluence of nine Indian river goddesses: Ganga, Yamuna, Sarasvati, Narmada, Godavari, Krishna, Tungabhadra, Kaveri, and Sarayu, states Diana Eck – a professor of Comparative Religion and Indian Studies. On the day of the Mahamaham festival, the river goddesses and Shiva gather here to rejuvenate their waters, according to a legend in the Periya Purana. The Hindus consider taking a pilgrimage and holy dip at the Mahamaham tirtha on the day of Mahamaham festival as sacred. The event attracts chariot processions, street fairs and classical dance performances in temple mandapas. The 12-year cycle Mahamaham festival in Tamil Nadu is observed in the Hindu calendar month of Magha, and is a symbolic equivalent of the Kumbh Mela.

Kumbakonam, or Kudanthai, is a city municipal corporation in the Thanjavur district in the Indian state of Tamil Nadu. It is located 40 km (25 mi) from Thanjavur and 282 km (175 mi) from Chennai and is the headquarters of the Kumbakonam taluk of Thanjavur district. It is the second largest city in the district after Thanjavur. The city is bounded by two rivers, the Kaveri River to the north and Arasalar River to the south. Kumbakonam is known as a "Temple town" due to the prevalence of a number of temples here and is noted for its Mahamaham festival, which happens once in 12 years, attracting people from all over the country.