The River Itchen is a chalk stream in Hampshire, one of only around 200 such rivers known globally, with 85% of the world's chalk streams found in the UK. It flows through Winchester and Southampton before entering Southampton Water, and is designated a Site of Special Scientific Interest (SSSI) due to its high-quality habitats. The river supports water voles, otters, white-clawed crayfish, kingfishers, butterflies, and dragonflies, with weeping willows and thick green hedgerows lining much of its banks.

For paddling purposes, the river divides into three distinct sections. The first is a freshwater ring of navigation in Winchester city centre, home to Winchester and District Canoe Club. The second is a freshwater stretch of approximately one and a half miles between Woodmill and Gaiters Mill, running alongside Riverside Park and tree-covered land up to Lower Itchen Country Park. The third and longest paddleable section is tidal, running approximately 4.5 miles from Woodmill downstream to where the river enters Southampton Water beneath the Itchen Bridge. A common starting point for the tidal section is Woodmill Plage (OS Grid Ref: SU 442 154, SO18 2JS), which offers car parking within 50 metres and easy access to the water.

The tidal section passes under several notable bridges including Cobden Bridge, a railway bridge, Northam Bridge, and the Itchen Bridge, and passes landmarks such as Northam Ocean Village Marina, the Southampton Water Activities Centre, Peartree Green, and the Vosper Thornycroft site. This section is rated at difficulty level 3 paddles and carries a significant safety consideration: the tidal river is busy with both commercial and recreational craft, requiring paddlers to remain vigilant at all times. The route can be paddled one way at approximately 4.5 miles, or as a round trip of around 9 miles by returning upriver.

Paddlers should be aware that access rights on non-tidal sections of the Itchen are not universally established. It is generally accepted that paddling is permitted as far upstream as Gaiters Mill. A British Canoeing membership may be relevant for licensing purposes on certain sections. The Itchen Navigation, a historic 10.4-mile disused canal system running from Winchester to Woodmill, is a related but separate waterway fed from the River Itchen.