The Sonepur Mela, also known as the Harihar Kshetra Mela, has quite a history behind it. According to mythology, it involves the story of King Indrayamuna and the Gandharva chief Huhu, who were transformed into an elephant and a crocodile respectively by the curse of great sages Agasthya and Dewala Muni. One day the elephant’s leg was caught by the crocodile. It is said that both of them fought hard for many years. But ultimately the elephant weakened and prayed to Vishnu (Hari) to save him. Vishnu heard his prayer and cut down the crocodile with his Chakra. But the touch of the chakra released Huhu from the curse. Vishnu also released Indrayamuna from his curse and took him to his abode, Vaikuntha. Since Sonepur is situated at the convergence of the sacred rivers Ganga and Gandak, it is regarded as a holy site. One of the purposes of the people visiting the Sonepur Cattle Fair, apart from the fair, is to take a holy dip at the convergence and pay respects at the Harihar Nath Temple.

The Harihar Nath Temple itself is believed to be built by Lord Ram while he was on his way to the Swayamvar of Sita. People also believe that the original temple was restored by Raja Man Singh. The present day temple is said to have been constructed by Raja Ram Narain, an influential prince during the Mughal period. The most recent repairs on the temple were undertaken by the Birlas.

According to the travelogue of W. W. Hunter, a British administrative officer, the Sonepur Mela used to be held in over 43 villages in the past. Chandragupta Maurya is said to have bought his elephants and horses from here. The mela used to attract traders from places as distant as Central Asia. Originally, the venue of the fair was Hajipur and only the performance of the puja used to take place at the

Harihar Nath Temple of Sonepur. However, under the rule of the Mughal emperor Aurangzeb, the venue of the fair was shifted to Sonepur.

As per the tradition, lakhs of Hindus from all over the country assemble at different ghats of Harihar Kshetra at Hajipur and Sonepur on the eve of Kartik Purnima and take holy dip at the confluence of the Ganga, the Gandak and the Mehi rivers. The full moon day of the month of Kartik (November) is regarded as one of the most auspicious days for the Hindus. The devotees offer Gangajal to the Harihar Nath Temple and this ritual marks the beginning of the Sonepur Mela.

Although, the Sonepur Cattle Fair remains the largest animal fair of its kind in Asia, it has become an integral part reflecting the social milieu of rural India. The fair attracts visitors from all over India who come to trade in various kinds of animals, the most important being elephants, cattle, and horses.
Sadly, flouting several laws, a lot of endangered species of animals are also traded which include Himalyan bears, several species of protected birds and reptiles. The fair also provides a good forum for folk artists and artisans who get to display and sell their handicrafts. The late evenings and nights acquire another dimension as the makeshift ‘theatres’ come alive with ribald noutonkis and blaring music replete with raunchy dances by nautch girls and plenty of ‘wardrobe malfunctions’!!