Southampton Water is a tidal estuary north of the Solent and the Isle of Wight in England. The city of Southampton lies at its most northerly point. Along its salt marsh-fringed western shores lie the New Forest villages of Hythe and "the waterside", Dibden Bay, and the Esso oil refinery at Fawley. On the slightly steeper eastern shore are the Southampton suburb of Weston, the villages of Netley and Hamble-le-Rice, and the Royal Victoria Country Park.
Together with the Solent, Southampton Water is world-renowned for yachting. It served as one of the sailing and motorboating venues for the 1908 Summer Olympics.
Geographically, Southampton Water is classified as a ria, or drowned valley, of the English Channel. It was formed by the rivers Test major, Itchen and Hamble minor which flow into it, and became an inlet of the sea at the end of the last ice age when sea levels rose, flooding many valleys in the south of England. In particular, it is likely that Southampton Water formed partly due to the submerging of the River Solent which previously flowed through the area, and of which the River Test, River Itchen and River Medina are thought to be tributaries.