Bahraich is a city and a municipal board in Bahraich district in the state of Uttar Pradesh, India. Located on the Saryu River, a tributary of the Ghaghara river, Bahraich is 125 kilometres north-east of Lucknow, the state capital. The districts of Barabanki, Gonda, Balrampur, Lakhimpur Kheri, Shravasti and Sitapur share boundaries with Bahraich. A factor which makes this town important is the international border shared with Nepal.

The Karnali River, called Ghaghara River in India, Mapcha Tsangpo in Tibet, and the lower Ghaghara in Awadh called Sarayu River, is a perennial trans-boundary river that originates in the northern slopes of the Himalayas in the Tibetan Plateau, cuts through the Himalayas in Nepal and joins the Sharda River at Brahmaghat in India. Together they form the Ghaghara River, a major left-bank tributary of the Ganges. With a length of 507 km (315 mi), it is the longest river in Nepal. The total length of the Ghaghara up to its confluence with the Ganges at Revelganj in Bihar is 1,080 km (670 mi). It is the largest tributary of the Ganges by volume and the second largest by length after Yamuna.