The Lymington River drains part of the New Forest in Hampshire in southern England. Numerous headwaters to the west of Lyndhurst give rise to the river, including Highland Water, Bratley Water and Fletchers Water. From Brockenhurst the river runs southwards to the Solent at Lymington.

The New Forest is one of the largest remaining tracts of unenclosed pasture land, heathland and forest in Southern England, covering southwest Hampshire and southeast Wiltshire. It was proclaimed a royal forest by William the Conqueror, featuring in the Domesday Book.