Kosi Region is a region in Bihar (India) and Nepal's Sunsari District. There are 4 districts in this region: Sunsari District, Saharsa District, Madhepura District and Supaul District. It consists of Kosi Division and Sunsari District. It is a subregion in Mithila. Its geographically capital is Supaul.
The name of Kosi region comes from Kosi River/Kausiki that flows through this region. The name kosi came from Kausiki.
Kosi Region have 4 districts:
Kosi Region has been a part of Mithila till ancient times. It was ruled by Videha in latter vedic period, Darbhanga Raj (Princily state) and many others. The Rive Kosi that flows thourh this region was also known as kausiki in Hindu mythologies.