The Baba Harihar Nath Mandir is a revered temple located in Sonepur, Bihar, near Patna. This temple is unique as it houses a Harihar Shivling, which is the only one in the world where half of the figure represents Lord Shiva (Hara) and the other half represents Lord Vishnu (Hari).

The temple is believed to have been established by Brahma himself to bring the Shaiva and Vaishnava sects closer together. According to legend, Lord Ram stayed here with Guru Vishwamitra on his way to Janakpur, and his footprints are worshiped at this site.

The temple attracts thousands of pilgrims, especially during the Sonepur Mela, which is organized every year in the month of Kartik (October-November). Taking a bath in the temple on Kartik Purnima is believed to yield the result of a hundred Godans.