Gorleston-on-Sea (/ˈɡɔːrlstən/), historically and colloquially known as Gorleston, is a seaside town in the borough of Great Yarmouth in Norfolk, England. It lies to the south of Great Yarmouth, on the opposite side of the mouth of the River Yare. Historically in Suffolk, it was a port town at the time of the Domesday Book. It was incorporated into Great Yarmouth in 1836. Gorleston's port became a centre of fishing for herring along with salt pans used for the production of salt to preserve the fish. In Edwardian times the fishing industry rapidly declined and the town's role changed to that of a seaside resort.

The place-name 'Gorleston' is first attested in the Domesday Book of 1086, where it appears as Gorlestuna. It appears as Gurlestona in the Pipe Rolls of 1130. The first element may be related to the word 'girl', and is probably a personal name. The name could mean "girls' town or settlement", or a variant thereof, similar to Girlington in West Yorkshire.

Historically the town was in the county of Suffolk. In the Middle Ages it had two manors, and a small manor called Bacons. The medieval church of St. Andrew stands in the town and by historical association gives its name to the Gorleston Psalter, an important example of 14th century East Anglian illuminated art. At the northern tip of the parish an area known as Southtown (also known as South Town or Little Yarmouth) grew as a suburb to Great Yarmouth, facing it across the Yare.

Gorleston Barracks were established in 1853. There were to be three railway stations in the town on the Yarmouth-Lowestoft Line. The stations on the line were Gorleston-on-Sea, Gorleston North and Gorleston Links which all closed between 1942 and 1970. The closest railway stations are now Lowestoft and Great Yarmouth.

Its main attraction is its sandy "Edwardian Beach." It has traditional seaside gardens and model boat pond. It also has a theatre opposite the pier called the Pavilion. The main shopping centre is on High Street. It has its own golf club. There is also the hospital and a library. There is a lighthouse, lifeboat station and coastwatch station on Riverside Road. In 2023 the beach was voted the best in Britain, and the 12th best in Europe, by Tripadvisor reviewers.

St Peter the Apostle Roman Catholic Church, built in 1938–39, was Eric Gill's only complete work of architecture.

In the Great Storm of 1987, Gorleston-on-Sea experienced the highest wind speed recorded in the UK on that day, which was 122 mph (196 km/h).

The town is meticulously described in the novel Gorleston by Henry Sutton (Sceptre, 1995) and in Philip Leslie's novels The History of Us (Legend Press, 2009) and What Remains (December House, 2013). Both Sutton and Leslie employ the actual names of roads and retail outlets in their work.

Gorleston-on-Sea's Pier Hotel and beach feature as a key location in Danny Boyle's 2019 film Yesterday.

Gorleston was an ancient parish in Suffolk. Southtown was brought within Great Yarmouth's borough boundaries in 1668, whilst remaining part of the parish of Gorleston. The rest of the parish was added to the constituency of Great Yarmouth in 1832 under the Parliamentary Boundaries Act 1832. Great Yarmouth's municipal borough boundaries were adjusted to match the constituency from 1 January 1836 under the Municipal Corporations Act 1835, since when Gorleston has been administered as part of Great Yarmouth. The borough of Great Yarmouth straddled Norfolk and Suffolk between 1668 and 1891, with the original town north of the Yare being in Norfolk and Gorleston south of the Yare being in Suffolk. The borough was placed entirely in Norfolk in 1891, although as a county borough Great Yarmouth provided its own county-level services, independent from Norfolk County Council.

Gorleston continued to form a civil parish within the borough of Great Yarmouth until 1974, although as an urban parish it had no separate parish council. In 1951 the parish had a population of 24,984. On 1 April 1974 the civil parish was abolished.

There are a number of primary schools in the area serving Gorleston and the wider locality. Secondary schools include Cliff Park Ormiston Academy, Lynn Grove Academy and Ormiston Venture Academy.

East Norfolk Sixth Form College is located in Gorleston. It is a major sixth form provider in Norfolk, attracting students from a wide area.

The East Anglian School for Deaf and Blind Children (for deaf children and for blind children) was established in Gorleston in 1912 and based there until it closed in 1985. During the Second World War the school was evacuated to Aberpergwm House in Glynneath, Wales. The headmaster's house in Gorleston was severely damaged by bombing in 1941.

• William Adams (1864–1913) highly decorated lifesaver and swimming instructor
• Georgie Aldous (born 1998) British social activist, model and influencer
• Jessica-Jane Applegate (born 1996) Paralympic swimmer and gold medalist
• Rowland Fisher (1885–1969) painter, mainly known for his seascapes
• William Fleming (1865–1954) highly decorated lifeboatman
• John Fuller, Baron Fuller (born 1968), British life peer created Baron Fuller, of Gorleston-on-Sea in the County of Norfolk by Letters Patent on 8 March 2024 and took his seat in the House of Lords on 12 March 2024.
• Stanley Charles Fuller (1907–1988) Norfolk's first Olympic Athlete, who competed at the 1932 Olympic Games in Los Angeles.
• Paul Derek Gibbs (born 1972) former footballer with approx. 200 club caps
• Peter Green (1946–2020) English blues rock guitarist and the founder of Fleetwood Mac. Green lived in Gorleston for a brief period in the early 1990s.
• Ralph Jones (1900–1944) Gorleston-born Australian soldier who was posthumously awarded the George Cross for gallantry
• Maurice Kaufmann (1927–1997) actor on stage, film and TV, married to Honor Blackman 1961–1975
• Myleene Klass (born 1978) TV presenter, musician, former member of pop group Hear'Say
• Gregg Lowe (born 1986) actor
• George William Manby (1765–1854) inventor of a life-saving mortar for shipwrecks, blue plaque on his house at 86 High Road.
• Campbell Archibald Mellon (1876–1955) painter and founder member of the Great Yarmouth and Gorleston Society of Artists
• Sammy Morgan (born 1946) former professional footballer, making over 260 appearances
• Kate Norgate (1853–1935) eminent historian and author. Norgate lived in Gorleston from 1921 until her death
• Kip Sabian (born 1992) professional wrestler, currently signed by American promotion, All Elite Wrestling
• Peter Simpson (born 1945) former professional footballer with 370 appearances for Arsenal F.C.
• Hannah Spearritt (born 1981) actress and former member of pop group S Club 7
• Henry Edward Sutton (born 1963) Senior Lecturer in Creative Writing at the University of East Anglia and award-winning crime novelist

• Gorleston F.C., a non-League football club who play at Emerald Park in Gorleston-on-Sea

• Norfolk Record Office Information Leaflet 33: Great Yarmouth, (Norwich: Norfolk Record Office, 2006)

• Blue Plaques in Gorleston
• Great Yarmouth – The Golden Mile
• Gorelston