Kumbh Mela is a mass Hindu pilgrimage of faith in which Hindus gather to bathe in a sacred or holy river. Traditionally, four fairs are widely recognized as the Kumbh Melas: the Prayagraj Kumbh Mela, Haridwar Kumbh Mela, the Nashik-Trimbakeshwar Simhastha, and Ujjain Simhastha. These four fairs are held periodically at one of the following places by rotation: Allahabad (Prayagraj), Haridwar, Nashik district (Nashik and Trimbak), and Ujjain. The main festival site is located on the banks of a river: the Ganges (Ganga) at Haridwar; the confluence (Sangam) of the Ganges and the Yamuna and the invisible Sarasvati at Allahabad; the Godavari at Nashik; and the Shipra at Ujjain. Bathing in these rivers is thought to cleanse a person of all their sins.

The festival is the largest peaceful gathering in the world, and considered as the "world's largest congregation of religious pilgrims".

The Maha Kumbh occurs after 12 Purna Kumbh Melas i.e. every 144 years.
The Kumbh Mela (sometimes specifically called Purna Kumbh or "full Kumbha"), occurs every 12 years at a given site. Kumbh Mela at Allahabad is celebrated approximately 3 years after Kumbh at Haridwar and 3 years before Kumbh at Nashik and Ujjain (both of which are celebrated in the same year or one year apart). Ardh Kumbh ("Half Kumbh") Mela occurs every 6 years.