The Hariharnath temple at Sonepur in Saran district is now more known for the great Sonepur mela on Kartik Purnima day. The origin of the Shiva temple at Sonepur known as Hariharnath is shrouded in mystery. A large section of orthodox Hindus believe that the temple was built by Rama on his way to Janakpur to win Sita. There is, however, no reference to this in the Ramayana. But that Rama passed this way is established. It is a fact that the whole of Tirhut division is imbued with the Rama-Sita cult and there are a large number of temples throughout the Tirhut division, consisting of Champaran, Saran, Muzaffarpur and Darbhanga (Mithila) districts, which commemorate the deeds of Rama, Sita, Valmiki, etc. It may be correct to assume that this Hariharnath temple might have originated in this manner. The present temple, however, is not old. There is not much of architecture.
The present temple was built by Raja Ram Narain, a noted figure of Bihar during the later Mughal period. The temple has been recently reconstructed by the Birlas. The temple of Hariharnath Mahadeo is the principle place of worship here but several smaller temples also receive the offerings of pilgrims. Among these are the Kali Asthan and the Panch Devata Mandir; the latter was built by a priestess who claimed to have built the temple with the offerings she received.