The whole concept of Hariharnath Kshetra Sonepur Mela started around the worship of lord Hariharnath (Vishnu & Shiva) for which people come to sonepur. This Mela is known largest cattle fare of Asia. The Sonepur Cattle Fair is held on Kartik Poornima (the full moon day) in the month of November in Sonepur, Bihar, on the confluence of river Ganges and Gandak. The day is supposed to be very auspicious for worship of Hariharnath.
It is also known as Harihar Kshetra Mela and it attracts visitors from all over Asia. it is the biggest cattle fair of Asia and stretches on from fifteen days to one month. It has its origins during ancient times. This is when Chandragupta Maurya(340 - 297 BCE) used to buy elephants and horses across the river Ganges. The Sonepur Cattle Fair once used to attract traders from places as distant as Central Asia. In 2018, the Fair started on 2th November 2018 and 3th December 2018.