The River Alt is a river in the county of Merseyside in England just north of Liverpool. The river begins near Huyton and flows about 28 km northeast to empty into the Irish Sea at the town of Hightown. Other towns along the river include Kirkby, Maghull and Formby. There are 75 km of tributary feeding the river. About 250,000 people live in the area around the river. The northern part of the river forms the boundary between the counties of Merseyside and Lancashire.