Tan Hill (grid reference SU080640) is a hill which lies just to the north of the village of Allington in the parish of All Cannings, Wiltshire, England.
Its summit is 294 metres (965 ft) above sea level and is the second highest point of the North Wessex Downs AONB hill range (the adjacent Milk Hill is 295 m high) and of Wiltshire. It is also the third highest point between Bristol and London. To the south, its adjoins Clifford's Hill.
On 23 August 2009, the BBC programme Countryfile featured an item on analysis by Ordnance Survey to determine whether Milk or Tan Hill is the highest. It was confirmed that Milk Hill is 26 centimetres (10.2 in) higher than Tan Hill.
Along the north side of Tan Hill runs a section of The Wansdyke, an earth rampart which runs east to west across much of southern England.
Tan Hill formerly had a white horse.
In April 2003, a Dotterel was present on the summit of Tan Hill. This bird species does not usually migrate through Britain until May.
Formerly, Tan Hill had a hill figure of a white horse, sometimes called the Tan Hill Donkey due its notably large head.
The truth about its existence was originally unknown, with the only direct evidence coming from author Kathleen Wiltshire, who in her book Wiltshire Folklore, published in 1975, wrote about the small donkey being still partly visible "on Tan Hill, though the legs have become quite overgrown... This pony or donkey is 75 feet from nose to tail, which stretches down much like that of the Uffington horse, and its head is very large.". She went on to write that in "the 'valley' between Tan Hill and Rybury Camp stands a miniature stone circle of nine upright sarsen stones about four feet in height, in the centre of which lies a prostrate stone, about the length of a man. A pathway leads up to the 'donkey' from the circle." The figure subsequently became known as Mrs Wiltshires Donkey. Whilst Wiltshire stated the hill figure resided on Tan Hill, another, later source states the figure resided on a "medium steep slope between Tan Hill and Ryebury Camp".