Course
 Map of the River Thames
From the outskirts of Greater London, the river passes London. In central London, the river forms one of the principal axes of the city, from the Palace of Westminster to the Tower of London. Once clear of central London, the river passes Greenwich and Dartford before entering the sea in a drowned estuary near Southend-on-Sea.
In terms of counties, the Thames rises in Gloucestershire, traditionally forming the county boundary, firstly between Gloucestershire and Wiltshire, between Berkshire on the south bank and Oxfordshire on the north, between Berkshire and Buckinghamshire, between Berkshire and Surrey, between Surrey and Middlesex, and between Essex and Kent. Before the 1974 boundary changes, the current boundary between Berkshire and Surrey was between Buckinghamshire and Surrey.
The area to the west of London is normally called the Thames Valley, whilst east of Tower Bridge development agencies and Ministers have taken to using the term Thames Gateway.
Catchment area and discharge
 The lower course of the Thames in 1840
The lower course of the Thames in 1840
The whole of the River Thames drains a catchment area of some 12,935 square km (4994 square miles) (or 15,343 square km (5924 square miles) if the River Medway is included as a tributary).[4]
See Rivers of Great Britain for a full list of tributaries.
The non-tidal section
Innumerable brooks, streams and rivers, within an area of 9948 Ock, Thame, Pang, Kennet, Loddon, Colne, Wey and Mole.
Between Maidenhead and Windsor, the Thames supports an artificial secondary channel, known as the Jubilee River, for flood relief purposes.
More than half the rain that falls on this catchment is lost to evaporation and plant growth. The remainder provides the water resource that has to be shared between river flows, to support the natural environment, and the community needs for water supplies to homes, industry and agriculture.
The tidal section
About 90 km from the sea, at Teddington, the river begins to exhibit tidal activity from the North Sea. This tidal stretch of the river is known as "the Tideway". London was reputedly made capital of Roman Britain at the spot where the tides reached in AD 43, but this spot has moved up river in the 2000 years since then. At London, the water is slightly brackish with sea salt. Below Teddington, the principal tributaries include the rivers Brent, Wandle, Effra, Westbourne, Fleet, Ravensbourne (the final part of which is called Deptford Creek), Lea, Darent and Ingrebourne.
The average discharge of the Thames grows up to approximately 66 m3/s (cumecs) at the end of its non-tidal section at Kingston upon Thames, a figure which is exceeded by some other British rivers (e.g. the Severn and the Tay). Indeed, if the Thames were not a tidal river, its average discharge in the centre of London would be somewhere between 80 and 100 m³/s, and the Thames would look like a small river, not the large river we can see today by Westminster, the Houses of Parliament or the City.
Navigation
 Bray lock, Berkshire
Bray lock, Berkshire
The River Thames is navigable from the estuary as far as Lechlade in Gloucestershire. Between the sea and Teddington Lock, the river forms part of the Port of London and navigation is administered by the London Authority">Port of London Authority. From Teddington Lock to the head of navigation, the navigation authority is the Environment Agency.
The river is navigable to large ocean-going ships as far as the Pool of London and London Bridge. Today little commercial traffic passes above the docks at Tilbury, and central London sees only the occasional visiting cruise ship or warship moored alongside HMS Belfast and a few smaller aggregate or refuse vessels operating from wharves in the west of London. Both the tidal river through London and the non-tidal river upstream are intensively used for leisure navigation.
There are 45 locks on the River Thames. See Locks on the River Thames for a full list of all locks.
Crossings
 Railway bridge at Maidenhead
Railway bridge at Maidenhead
The River Thames is crossed by many bridges and tunnels. Famous crossings of the Thames include:
Dartford Crossing
Thames Barrier
Blackwall Tunnel
Rotherhithe Tunnel
Thames Tunnel
Tower Bridge
London Bridge
Millennium Bridge
Hungerford Bridge
Westminster Bridge
Maidenhead Railway Bridge
Marlow Bridge
See Crossings of the River Thames for a full list of all crossings.
Islands
 Sunset on the river Thames viewed from Greenwich
Sunset on the river Thames viewed from Greenwich
Famous islands in the Thames include:
Isle of Sheppey
Canvey Island
Isle of Grain
Eel Pie Island, Twickenham
Magna Carta Island, Runnymede
Reading (sometimes known as De Montfort Island)
See Islands in the River Thames for a full list of all islands.
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