Etymology: Proto-Celtic *tamēssa, possibly meaning "dark"

Country: England

Counties: Gloucestershire, Wiltshire, Oxfordshire, Berkshire, Buckinghamshire, Surrey, Greater London, Kent, Essex

Towns/cities: Cricklade, Lechlade, Oxford, Abingdon, Wallingford, Reading, Henley-on-Thames, Marlow, Maidenhead, Windsor, Staines-upon-Thames, Walton-on-Thames, Sunbury-on-Thames, Kingston upon Thames, London (inc. Twickenham, the City), Dagenham, Erith, Dartford, Grays, Gravesend

Mouth: Thames Estuary, North Sea

Length: 215 mi (346 km)

Basin size: 12,935 km² (4,994 sq mi)