Chertsey is a town in the Borough of Runnymede, Surrey, England, 29 km (18 mi) south-west of central London. It grew up round Chertsey Abbey, founded in 666 CE, and gained a market charter from Henry I. A bridge across the River Thames first appeared in the early 15th century.

The River Bourne through the town meets the Thames at Weybridge. The Anglican church has a medieval tower and chancel roof. The 18th-century listed buildings include the current stone Chertsey Bridge and Botleys Mansion. A curfew bell, rung at 8 pm on weekdays from Michaelmas to Lady Day ties with the romantic local legend of Blanche Heriot, marked by a statue of her and the bell at Chertsey Bridge. Green areas include the Thames Path National Trail, Chertsey Meads and a round knoll (St Ann's Hill) with remains of a prehistoric hill fort known as Eldebury Hill. Pyrcroft House dates from the 18th century and Tara from the late 20th. Train services are run between Chertsey railway station and London Waterloo by South Western Railway. The town is within the M25, accessible via junction 11.

The first written mention of Chertsey is by Bede c. 750, in which he describes the location as Cerotaesei, id est Ceroti insula (translated as "Chertsey, that is the island of Cerotus"). The settlement appears in 13th-century copies of 7th-century charters as Cirotesige, Cirotesge and Cerotesge. The manor is recorded as Certesi in Domesday Book in 1086 and as Certeseye in 1129-30. Other later forms include Charteseye (mid-14th century), Charsey (in 1543) and Chutsey (in 1606). The first use of the modern spelling "Chertsey" is from 1559.

The first part of the toponym "Chertsey" is thought to refer to a Celtic individual, whose name was subsequently Latinised to Cerotus. The second part derives from the Old English eg and means "island or well-watered land".

Chertsey Bridge is a Scheduled Ancient Monument and Grade II* listed structure that has a listed City (of London tax) Post at one end, and nearby milestones. It is predominantly of ashlar light stone with two white flagstone york stone pavements with a low weight limit and narrow carriageways inappropriate to HGVs, which have Staines Bridge, Walton Bridge or motorway alternatives to reach Spelthorne.

Samuel Lewis included it in his opening description of the town above: "...[River Thames] over which is a handsome stone bridge of seven arches, built in 1785, at an expense of £13,000, defrayed jointly by the counties of Surrey and Middlesex..." It was built in 1783-1785 by James Paine.

Chertsey has an admission-free museum on Windsor Street, which provides considerable information about the history of Chertsey. The museum holds the Olive Matthews costume collection, which is of national importance, contains around three thousand pieces of costume and was donated by Matthews to the museum in 1969.

The museum contains clocks by two local makers, James Douglass and Henry Wale Cartwright. (Note however that there were three successive watchmakers called James Douglass (or Douglas) in the Douglas family, the latter based in Egham).