Flint mines and Stone Age artefacts have been found in the surrounding countryside of the Eastbourne Downs.
Celtic people are believed to have settled on the Eastbourne Downland in 500BC.
There are Roman remains buried beneath the town, such as a Roman bath and section of pavement between Eastbourne Pier and the Redoubt Fortress. There is also a Roman villa near the entrance to the Pier and the present Queens Hotel.
In 2014, skeletal remains of a woman who lived around 425AD were discovered in the vicinity of Beachy Head on the Eastbourne Downland Estate. The remains were found to be of a 30-year-old woman who grew up in East Sussex, but had genetic heritage from sub-Saharan Africa, giving her black skin and an African skeletal structure. Her ancestors came from below the Saharan region, at a time when the Roman Empire extended only as far as North Africa.
An Anglo-Saxon charter, circa 963 AD, describes a landing stage and stream at Burne.
The original name came from the 'Burne' or stream which ran through today's Old Town area of Eastbourne. All that can be seen of the Burne, or Bourne, is the small pond in Motcombe Gardens. The bubbling source is guarded by a statue of Neptune. Motcombe Gardens are overlooked by St. Mary's Church, a Norman church which allegedly lies on the site of a Saxon ‘moot’, or meeting place. This gives Motcombe its name.
In 2014 local metal-detectorist Darrin Simpson found a coin minted during the reign of Æthelberht II of East Anglia (died 794), in a field near the town. It is believed that the coin may have led to Æthelberht's beheading by Offa of Mercia, as it had been struck as a sign of independence. Describing the coin, expert Christopher Webb, said, "This new discovery is an important and unexpected addition to the numismatic history of 8th century England." 
Following the Norman conquest, the Hundred of what is now Eastbourne, was held by Robert, Count of Mortain, William the Conqueror's half brother. The Domesday Book lists 28 ploughlands, a church, a watermill, fisheries and salt pans.
The Book referred to the area as 'Borne'. 'East' was added to ‘Borne’ in the 13th century, renaming the town.
St Mary's Church, Old Town, Eastbourne
A charter for a weekly market was granted to Bartholomew de Badlesmere in 1315–16; this increased his status as Lord of the Manor and improved local industry. During the Middle Ages the town was visited by King Henry I and in 1324 by Edward II. Evidence of Eastbourne's medieval past can seen in the 12th century Church of St Mary, and the manor house called Bourne Place.
In the mid-16th century Bourne Place was home to the Burton family, who acquired much of the land on which the present town stands. This manor house is currently owned by the Duke of Devonshire and was extensively remodelled in the early Georgian era when it was renamed Compton Place. It is one of the two Grade I listed buildings in the town.
Eastbourne has Cornish connections, most notably visible in the Cornish high cross in the churchyard of St Mary's Church which was brought from an unspecified location in Cornwall.
In 1752, a dissertation by Doctor Richard Russell extolled the medicinal benefits of the seaside. His views were of considerable benefit to the south coast and, in due course, Eastbourne became known as "the Empress of Watering Places".
Eastbourne's earliest claim as a seaside resort came about following a summer holiday visit by four of King George III's children in 1780 (Princes Edward and Octavius and Princesses Elizabeth and Sophia).
In 1793, following a survey of coastal defences in the southeast, approval was given for the positioning of infantry and artillery to defend the bay between Beachy Head and Hastings from attack by the French. Fourteen Martello Towers were constructed along the western shore of Pevensey Bay, continuing as far as Tower 73, the Wish Tower at Eastbourne. Several of these towers survive: the Wish Tower is an important feature of the town's seafront and was the subject of a painting by James Sant RA, and part of Tower 68 forms the basement of a house on St. Antony's Hill. Between 1805 and 1807, the construction took place of a fortress known as the Eastbourne Redoubt, which was built as a barracks and storage depot, and armed with 10 cannons.
A connection with India comes in the shape of the 18th-century Lushington monument, also at St Mary's, which commemorates a survivor of the Black Hole of Calcutta atrocity which led to the British conquest of Bengal.
Bourne Stream running through Motcombe Gardens
Eastbourne remained an area of small rural settlements until the 19th century.
Four villages or hamlets occupied the site of the modern town: Bourne (or, to distinguish it from others of the same name, East Bourne), is now known as Old Town, and this surrounded the bourne (stream) which rises in the present Motcombe Park; Meads, where the Downs meet the coast; South Bourne (near the town hall); and the fishing settlement known simply as Sea Houses, which was situated to the east of the present pier.
By the mid-19th century most of the area had fallen into the hands of two landowners: John Davies Gilbert (the Davies-Gilbert family still own much of the land in Eastbourne and East Dean) and William Cavendish, Earl of Burlington.
The Gilbert family's holdings date to the late 17th and early 18th centuries when barrister Nicholas Gilbert married an Eversfield and Gildredge heiress. (The Gildredges owned much of Eastbourne by 1554. The Gilberts eventually made the Gildredge Manor House their own. Today the Gildredge name lives on in the eponymous park.)
Trevithick, the inventor of the steam locomotive (a claim disputed on the grave of one Vyvyan in the churchyard at Camborne), is reported to have spent some time here.
An early plan, for a town named Burlington, was abandoned, but on 14 May 1849 the London, Brighton and South Coast Railway arrived to scenes of great jubilation. With the arrival of the railway, the town's growth accelerated.
Cavendish, now the 7th Duke of Devonshire, recruited Henry Currey in 1859 to lay out a plan for what was essentially an entire new town – a resort built "for gentlemen by gentlemen". The town grew rapidly from a population of less than 4,000 in 1851 to nearly 35,000 by 1891. In 1883, it was incorporated as a municipal borough; a purpose-built town hall was opened in 1886. This period of growth and elegant development continued for several decades. A royal visit by
George V and Queen Mary in March 1935 is commemorated by a plaque on chalet number 2 at Holywell.
During the First World War, Summerdown Camp, a convalescent facility, opened in 1915 near the South Downs to treat soldiers who were injured during trench warfare or seriously ill. It was the largest of this type in the UK during this war, treating 150,000; 80% were able to return to fight. The facility was dismantled in 1920. An exhibition about the history of the camp was held in Eastbourne for several months in 2015.
In 1926, the Eastbourne Corporation Act enabled the creation of the Eastbourne Downland Estate.
The Second World War saw a change in fortunes. Initially, children were evacuated to Eastbourne on the assumption that they would be safe from German bombs, but soon they had to be evacuated again because after the fall of France in June 1940 it was anticipated that the town would lie in an invasion zone. Part of Operation Sea Lion, the German invasion plan, envisaged landings at Eastbourne. Many people sought safety away from the coast and shut up their houses. Restrictions on visitors forced the closure of most hotels, and private boarding schools moved away. Many of these empty buildings were later taken over by the services. The Royal Navy set up an underwater weapons school, and the Royal Air Force operated radar stations at Beachy Head and on the marshes near Pevensey. Thousands of Canadian soldiers were billeted in and around Eastbourne from July 1941 to the run-up to D-Day. The town suffered badly during the war, with many Victorian and Edwardian buildings damaged or destroyed by air raids. Indeed, by the end of the conflict it was designated by the Home Office to have been ‘the most raided town in the South East region’. The situation was especially bad between May 1942 and June 1943 with hit–and–run raids from fighter–bombers based in northern France.
In the summer of 1956 the town came to national and worldwide attention, when Dr John Bodkin Adams, a general practitioner serving the town's wealthier patients, was arrested for the murder of an elderly widow. Rumours had been circulating since 1935 regarding the frequency of his being named in patients' wills (132 times between 1946 and 1956) and the gifts he was given (including two Rolls Royces). Figures of up to 400 murders were reported in British and foreign newspapers, but after a controversial trial at the Old Bailey which gripped the nation for 17 days in March 1957, Adams was found not guilty. He was struck off for four years but resumed his practice in Eastbourne in 1961. According to Scotland Yard's archives, he is thought to have killed up to 163 patients in the Eastbourne area.
Eastbourne from Lord G. Cavendish's Seat in the Park
, John Nixon, 1787
After the war, development continued, including the growth of Old Town up the hillside (Green Street Farm Estate) and the housing estates of Hampden Park, Willingdon Trees and Langney. During the latter half of the 20th century, there were controversies over the demolition of Pococks, a 15th-century manor house on what is now the Rodmill Housing Estate, and the granting of planning permission for a 19-storey block at the western end of the seafront. The latter project (South Cliff Tower) was realised in 1965 despite a storm of protest led by the newly formed Eastbourne and District Preservation Committee, which later became Eastbourne Civic Society, and was renamed the Eastbourne Society in 1999. Local conservationists also failed to prevent the construction of the glass-plated TGWU conference and holiday centre, but were successful in purchasing Polegate Windmill, thus saving it from demolition and redevelopment. Most of the expansion took place on the northern and eastern margins of the town, gradually swallowing surrounding villages. However, the richer western part was constrained by the Downs and has remained largely unchanged. In 1981, a large section of the town centre was replaced by the indoor shops of the Arndale Centre.
In the 1990s, both growth and controversy accelerated rapidly as a new plan was launched to develop the area known as the Crumbles, a shingle bank on the coast to the east of the town centre. This area, now known as Sovereign Harbour, containing a marina, shops and several thousand houses, along with luxury flats, was formerly home to many rare plants. There has been continued growth in other parts of the town, and the central marshland has become farmland and nature reserves.
In 2009, the new Towner Gallery was opened, abutting the listed Congress Theatre built in 1963.
In 2016–17 extensive remodelling work was undertaken to the prominent Arndale Centre, which takes up most of the town centre, and was originally built by Legal & General Assurance in the 1980s.
Local History Society
Eastbourne Local History Society was founded in 1970. It is a charitable, not-for-profit organisation in the United Kingdom whose objective is the pursuit and encouragement of an active interest in the study of the history of Eastbourne and its immediate environs and the dissemination of the outcome of such studies.
As the major landowner, the Cavendish family has had strong connections with Eastbourne since the 18th century. The current President of the Society is William Cavendish, Earl of Burlington.
Containing over 1,500 articles about the history of Eastbourne, the Society's indexed journal, The Eastbourne Local Historian, is the major historical resource for the town and has been published quarterly since its inception in 1970. Over the years, the Society has published various books about the history of Eastbourne, seven of which are currently in print.