The name Morang is derived from the name of the Limbu King Mawrong Mung Hang, who established Morang Kingdom in the beginning of seventh century. His capital and fort was at Rongli, present day Rangeli. Morang was then annexed to greater Limbuwan by King Uba hang in 849 CE and ruled until 1584 CE when Limbu King Sangla Ing made Morang independent and ruled from Varatappa situated east of Modern Bijaypur. The Ing Dynasty and followed by Sen dynasty then Khebang dynasty ruled Morang until 1774 CE. Morang name fell from use after the annexation of all the Kingdoms of Limbuwan including Morang by King Prithivi Narayan Shah of Gorkha. The last King of Morang was Buddhi Karna Raya Khebang, who ruled from Bijaypur near Dharan.
The Kingdom of Morang, until its annexation to the Gorkha Kingdom of King Prithivi Narayan Shah, comprised all the terai lands east of the Koshi River and west of the Mechi River.
The name Morang came into use again after the shah kings divided the country into administrative districts and Morang was named after the old Morang Kingdom.