The River Hiz is a small tributary river in Hertfordshire that feeds the River Ivel that, in turn, feeds the River Great Ouse. Starting at its source of a chalk fed spring just south of the village of Charlton, the river winds its way through the county of Hertfordshire, moving its way into and through Hitchin, where it meets the River Oughton and River Purwell. The Hiz finally meets the River Ivel near the village of Henlow.