Horley is not recorded in the Domesday Survey of 1086 and it is first mentioned in surviving documents in the late 12th century. Various suggestions have been put forward as to the meaning of the name, but it probably derives from 'Hornelye'- 'clearing belonging to Horne'. Indeed, the name is written as 'Hornelye', 'Horneleya' and 'Hornele' in 14th and 15th century documents. The parish church of St Bartholomew still has a few 14th century features, but much more was destroyed during extensive work undertaken on the church in the early 1880s.

Horley belonged to Chertsey Abbey until the abbey was dissolved by Henry VIII in 1537. In that same year Henry granted Horley to Sir Nicholas Carew. Carew was executed for treason and Henry then gave Horley to Sir Robert Southwell in 1539 but Sir Robert sold it five years later to Robert Bristowe. However, by 1598 the manor was back with the Carew family. Two years later Matthew Carew conveyed the manor to James Cromer who, in 1602, passed it to the governors of Christ's Hospital.

The transformation of Horley from an insignificant village to a town began in 1841 when the railway from London to Brighton was opened. It passed close to the village and a station was provided . The station was re-sited in 1905. At nearby Gatwick there was an important racecourse which opened in 1891 complete with its own station. The Grand National was run here during the First World War when Aintree, near Liverpool, was in use by the military.

In 1930 a small airfield was laid out adjacent to the racecourse - the flat land here was ideal for the purpose. Eventually this airfield was to swallow up the racecourse and develop as London's second international airport.

The close proximity of Horley to the airport in modern times has brought new residents to the town, attracted by the employment opportunities at a facility now used by millions of travellers each year.