River Thames

The River Thames (ⁱ/tɛmz/ TEMZ) is a river that flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom, after the River Severn. While it is best known for flowing through London, the river also flows alongside other towns and cities, including Oxford, Reading, Henley-on-Thames and Windsor.

The river gives its name to three informal areas: the Thames Valley, a region of England around the river between Oxford and West London; the Thames Gateway; and the greatly overlapping Thames Estuary around the tidal Thames to the east of London and including the waterway itself. Thames Valley Police is a formal body that takes its name from the river, covering three counties.

In an alternative name, derived from its long tidal reach up to Teddington Lock in south west London, the lower reaches of the river are called the Tideway. The section of the river running through Oxford is traditionally called the Isis.

The administrative powers of the Thames Conservancy have been taken on with modifications by the Environment Agency and, in respect of the Tideway part of the river, such powers are split between the agency and the Port of London Authority.