The Karamnasa or Karmanasa River is a tributary of the Ganges. It originates in Kaimur district of Bihar and flows through the Indian states of Uttar Pradesh and Bihar. Along the boundary between Uttar Pradesh and Bihar it has the districts of Sonbhadra, Chandauli, Varanasi and Ghazipur on its left ; and the districts of Kaimur and Buxar on its right.