Biratnagar dates back to the beginning of the 7th century, when King Mung Mawrong Hang came to prominence in the terai lands of Limbuwan (present-day Sunsari, Morang, and Jhapa areas). He cleared much of the forest area in present-day Rangeli, east of Biratnagar, and built a town there. He named his Kingdom Morang after his name and rose to power.

The old name of Biratnagar was Gograha Bazaar.