River · United Kingdom
River Thames
The Thames is the longest river that flows entirely in England. It begins as a spring in the Cotswold Hills, flows past Oxford, Reading and Windsor and runs through London before it reaches the North Sea.
Picture credit: Zxb (CC BY-SA 2.0 at) · mattbuck (CC BY-SA 3.0) · Wikimedia Commons
Where is River Thames?
The river starts here: Thames Head near Kemble, Cotswolds, Gloucestershire.
It ends in the North Sea (Thames Estuary) near Southend-on-Sea.
Countries on the river: the United Kingdom.
The story behind it
In Oxford the Thames is sometimes called the Isis, and rowers from Oxford and Cambridge race each other on the river in the famous Boat Race. On their way downstream, boats pass through 45 locks, a kind of water staircase. Long ago, in very cold winters, the river froze in London, and people held Frost Fairs on the ice with tents and games; the first was in 1607 and the last in 1814. In 1858 the river smelled so bad that the summer was called the Great Stink. Later the Thames was even declared biologically dead. Today it is much cleaner: seahorses, harbour porpoises and more than 1 000 seals, counted on sandbanks in 2024, live in its estuary. Each year the swans on the river are counted in an old tradition called Swan Upping. To protect London from floods coming in from the sea, the huge gates of the Thames Barrier can be closed.
Questions children ask
How long is the River Thames?
The River Thames is about 346 km long. It flows from Thames Head in the Cotswolds to the North Sea near Southend-on-Sea.
Is the Thames the longest river in the United Kingdom?
No, the longest is the River Severn, and the Thames comes second. But the Thames is the longest river that flows entirely in England.
What is the Thames Barrier?
The Thames Barrier is a flood barrier across the river at Woolwich in London, 523 metres long with 10 movable gates. Since the 1980s it has protected London from floods coming up the river from the sea.
Where these numbers come from
Every figure on this page was checked against public reference sources before publication. Where sources genuinely disagree, the text says so.
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