Bagaha is a city and a municipality in the district of West Champaran in the state of Bihar, India. It is the headquarters of the Bagaha subdivision and also functions as a Police District. The town is situated on the banks of the Gandak River, approximately 64 kilometres (40 mi) northwest of the district headquarters Bettiah, and 294 kilometres (183 mi) from the state capital Patna. It lies close to the Valmiki Tiger Reserve and the India–Nepal border.