Domariaganj is a town and tehsil of Siddharthnagar district in eastern Uttar Pradesh.Domariaganj is a town in the North East of Uttar Pradesh, India. It is located on the bank of the river Rapti, 30 km south of the Nepal border.Domariaganj Lok Sabha constituency (Hindi: डुमरिया गंज लोक सभा निर्वाचन क्षेत्र) is one of the 80 Lok Sabha (parliamentary) constituencies in Uttar Pradesh state in northern India.