Slough (pronounced /ˈslaʊ/ (listen), rhymes with 'cow'), situated 19 miles (31 km) west of Charing Cross, is a borough and unitary authority within the ceremonial county of Berkshire, England. At the time of the 2001 census, the population of Slough was 119,070 (est. 122,000 in 2006) and the borough area was the most ethnically diverse local authority area outside London in the United Kingdom.

Historically, the larger part of the present-day Slough area was formerly in Buckinghamshire with a small part of the borough originally in Middlesex. Slough is home to the Slough Trading Estate, which, coupled with extensive transport links, makes it an important business centre in South East England. It is also home to a campus of Thames Valley University.

The first recorded uses of the name occur as Slo in 1196, Sloo in 1336, and Le Slowe, Slowe or Slow in 1437. It first seems to have applied to a hamlet between Upton to the east and Chalvey to the west, roughly around the "Crown Crossroads" where the road to Windsor (now the A332) met the Great West Road.The Domesday Survey of 1086 refers to Upton, and a wood for 200 pigs, worth £15. During the 13th century, King Henry III had a palace at Cippenham. Parts of Upton Court were built in 1325, while St Mary's Church in Langley was probably built in the late 11th or early 12th century, though it has been rebuilt and enlarged several times.

From the mid 17th century, stagecoaches began to pass through Slough and Salt Hill, which became locations for the second stage to change horses on the journey out from London. By 1838 and the opening of the Great Western Railway, Upton-cum-Chalvey's parish population had reached 1,502. In 1849, a branch line was completed from Slough station to Windsor and Eton Central railway station, opposite Windsor Castle, for the Queen's convenience.

Slough has 96 listed buildings.There are four Grade I: St Laurence's Church (Upton), St Mary the Virgin's church (Langley), Baylis House and Godolphin Court; seven Grade II*: St Mary's Church (Upton-cum-Chalvey), Upton Court, the Kederminster and Seymour Almshouses in Langley, St Peter's Church (Chalvey), The Ostrich Inn (Colnbrook), and King John's Palace (Colnbrook); and Grade II listed structures include four milestones, Slough station, and Beech, Oak and Linden Houses at Upton Hospital.

1918 saw a large area of agricultural land to the west of Slough developed as an army motor repair depot, used to store and repair huge numbers of motor vehicles coming back from the battlefields of the First World War in Flanders. In April 1920 the Government sold the site and its contents to the Slough Trading Co. Ltd. Repair of ex-army vehicles continued until 1925 when the Slough Trading Company Act was passed allowing the company (renamed Slough Estates Ltd) to establish an Industrial Estate.

Spectacular growth and employment ensued, with Slough attracting workers from many parts of the UK and abroad.

After the Second World War, several further large housing developments arose to take large numbers of people migrating from war-damaged London.