The River Alre (also, occasionally, Arle) is a tributary of the River Itchen in Hampshire in the south of England. It rises in Bishop's Sutton and flows west for 6 km (3.7 mi) to meet the Itchen below New Alresford. The river is a classic English chalk stream with a shallow gravel bed and fast flowing waters, fed year-round by chalk springs. Through Bishop's Sutton it forms a good natural trout fishery and later supports a watercress harvest after which the Watercress Line, a heritage steam railway, is named.