Painshill (formally Painshill Park) is a restored, 18th-century English park and landscape garden in Cobham, Surrey, England. It was created between 1738 and 1773 by the owner, Charles Hamilton, from an area of heathland and woodland. Painshill is laid out as a series of scenes, crafted by combining architectural features with trees and shrubs, many of which are non-native species. Several of the surviving follies are listed in their own right, including the Gothic Tower, at the western end of the park, and the Gothic Temple, which overlooks the northern part of the lake. The Grotto, the largest in England, is decorated with crystalline mineral stones, including quartz, feldspar and Blue John.

In designing Painshill, Hamilton was influenced by 17th-century landscape artists, whose works he had encountered on Grand Tours in continental Europe. Instead of trying to replicate specific artworks, Hamilton used the techniques of landscape painting to create scenes with contrasting emotional tones – from the solemnity of the dark evergreens surrounding the Mausoleum, to the brighter trees and flowers at the Temple of Bacchus. Advocates of the Picturesque were complimentary of Hamilton's work, particularly the hillier, western half of the park, which Horace Walpole likened to a "kind of Alpine scene". International visitors to the park and garden included John Adams, the future American president, who wrote that "Paines Hill is the most striking piece of art that I have yet seen."

Hamilton borrowed heavily to finance his work and was forced to sell Painshill in 1773. The estate passed through a series of private owners until the Second World War, when it was requisitioned for military use. In the late 1940s, it was divided into lots and parts were used for commercial forestry and pig farming. The architectural features began to decay and much of the land became overgrown. Concerns over the condition of the park were voiced in the following decades, leading to the purchase of over 150 acres (61 hectares) by Elmbridge Borough Council in the late 1970s and early 1980s. In June 1984, around 212 acres (86 ha) of Hamilton's original estate was designated a Grade I Park and Garden on the register of historic parks and gardens maintained by Historic England.

Restoration of Painshill began in the early 1980s, with the aim of reinstating Hamilton's original design wherever possible. Surviving architectural features, including the Gothic Temple and Ruined Abbey, were restored, and those that had disappeared completely, such as the Turkish Tent and the Hermitage, were reconstructed. The part of the park owned by the borough council was reopened to the public on summer weekends from mid-May 1989 and seven-days-a-week from April 1997. In January 1999, the park was awarded a Europa Nostra medal for its "exemplary restoration", and in May 2006, the plantation of non-native trees on the Chinese Peninsula was awarded "national collection status" by the National Council for the Conservation of Plants and Gardens. Since 2000, Painshill has been used as a filming location for the feature films Dorian Gray and Suffragette and for the television series Black Mirror and Bridgerton.

The earliest surviving record of Painshill is from 1548, when it appears as Payneshill in a Land Registry manuscript. The area may have been named after the Payne family, who owned part of the land in the late Middle Ages. A "Richard Payne" appears in the 1263 assizes documents and the name "John Payne" can be found in local subsidy rolls from 1332. In the 16th century, the area surrounding Painshill House was recorded as the "Painshill common field" and "The Paynes Hawe".

Painshill was originally part of the manor of Walton-on-Thames, but had become separate by 1512, when a portion of the land was conveyed to Richard Foxe, then Bishop of Winchester. Foxe transferred his holding to Corpus Christi College, Oxford, which he founded in 1517. In 1539, Henry VIII expanded the Chase of Hampton Court, incorporating "parte of the Towne or Village of Cobham in the Countie of Surrie". A survey of the chase from around 1540 identifies six areas within Painshill owned by the Crown, including the "Greate grove", of around 40 acres (16 hectares), and "hale hill", the future site of the Grotto.

Henry VIII died in 1547 and Painshill was subsequently divided into plots and leased. The two largest areas, the "Tenement at Payneshill" and the "Tenement at Coveham Bridge", became a single holding in 1570. Comprising around 97+1⁄2 acres (39 ha), the united tenement forms the core of the land at Painshill owned by Elmbridge Borough Council. A survey of March 1649 suggests that part of the area was being used as arable farmland, although there were still significant areas of woodland. There is also a record of a warren at Painshill in the 17th century.

At the start of the 18th century, Painshill was divided between land leased from the Crown by Robert Gavell and a freehold property owned by the Smyther family. Gabriel, Marquis du Quesne, bought the Smythers' land in around 1717, by which time it consisted of two or three farms. Du Quesne is thought to have built a house and laid out a small garden, but he was ruined as a result of the collapse of the South Sea Company in 1720 and he sold Painshill to William Bellamy in 1725. Bellamy, a barrister at the Inner Temple, also started to lease the land owned by the Crown, which had become available following the death of Gavell in 1724.