This paper reports on the impact of mass bathing on Ganga River water quality on the occasion of the Maha-Shivaratri festival at Haudeshwarnath Ghat situated on the left bank of the River Ganga in the district of Pratapgarh, India. Water samples collected from three sampling points before and after mass bathing were analysed for a total of 17 physico-chemical and seven biological parameters. It was concluded from the results that mass bathing causes a significant change in water quality of the river, which may represent a health hazard to users of the river water.