The area has been occupied since the
Palaeolithic era, as attested by finds from the quarries at
Medway megaliths were built during the
Neolithic era. There is a rich sequence of
Iron Age, and
Roman era occupation, as indicated by finds and features such as the
Ringlemere gold cup and the Roman villas of the
The modern name of Kent is derived from the
Brythonic word Cantus meaning "rim" or "border". This describes the eastern part of the current county area as a border land or coastal district.
Julius Caesar had described the area as Cantium, or home of the
Cantiaci in 51 BC.
 The extreme west of the modern county was by the time of
Roman Britain occupied by Iron Age tribes, known as the
East Kent became a kingdom of the
Jutes during the 5th century
 and was known as Cantia from about 730 and recorded as Cent in 835. The early medieval inhabitants of the county were known as the Cantwara, or Kent people. These people regarded the city of Canterbury as their capital.
Pope Gregory I appointed the religious missionary (who became
Saint Augustine of Canterbury after his death) as the first
Archbishop of Canterbury. In the previous year, Augustine successfully converted the
Æthelberht of Kent to Christianity. The
Diocese of Canterbury became Britain's first
Episcopal See with first cathedral and has since remained England's centre of Christianity.
 The second designated English cathedral was in Kent at
In the 11th century, the people of Kent adopted the motto
Invicta, meaning "undefeated". This naming followed the invasion of Britain by
William of Normandy. The Kent people's continued resistance against the
Normans led to Kent's designation as a semi-autonomous
county palatine in 1067. Under the nominal rule of William's half-brother
Odo of Bayeux, the county was granted similar powers to those granted in the areas bordering
 Kent was traditionally
partitioned into East and West Kent, and into lathes and hundreds.
During the medieval and early modern period, Kent played a major role in several of England's most notable rebellions, including the
Peasants' Revolt of 1381, led by
Jack Cade's Kent rebellion of 1450, and
Wyatt's Rebellion of 1554 against Queen
Title page of
's Perambulation of Kent
(completed in 1570, and published in 1576), a historical description of Kent and the first published
Royal Navy first used the
River Medway in 1547. By the reign of
Elizabeth I (1558–1603) a small dockyard had been established at
Chatham. By 1618, storehouses, a
drydock, and houses for officials had been built downstream from Chatham.
By the 17th century, tensions between Britain and the powers of the Netherlands and France led to increasing military build-up in the county. Forts were built all along the coast following the
raid on the Medway, a successful attack by the Dutch navy on the shipyards of the
Medway towns in 1667.
The 18th century was dominated by wars with France, during which the Medway became the primary base for a fleet that could act along the Dutch and French coasts. When the theatre of operation moved to the
Atlantic, this role was assumed by
Plymouth, with Chatham concentrating on shipbuilding and ship repair. As an indication of the area's military importance, the first
Ordnance Survey map ever drawn was a one-inch map of Kent, published in 1801.
 Many of the
Georgian naval buildings still stand.
In the early 19th century, smugglers were very active on the Kent coastline. Gangs such as
The Aldington Gang brought spirits, tobacco and salt to the county, and transported goods such as wool across the sea to France.
In 1889, the
County of London was created and the townships of
Lewisham were transferred out of Kent and in 1900 the area of
Penge was gained. Some of Kent is contiguous with the
Greater London sprawl, notably parts of
During World War II, much of the
Battle of Britain was fought in the skies over the county. Between June 1944 and March 1945, over 10,000
V1 flying bombs or "Doodlebugs", were fired toward London from bases in
Northern France. Although many were destroyed by aircraft, anti-aircraft guns, and
barrage balloons, both London and Kent were hit by around 2,500 of these bombs.
After the war, Kent's borders changed several more times. In 1965 the London boroughs of
Bexley were created from nine towns formerly in Kent.
 In 1998, Rochester, Chatham, Gillingham, and
Rainham left the administrative county of Kent to form the
Unitary Authority of
Medway. During this reorganisation, through an "apparent" administrative oversight, the city of Rochester lost its official
 In 2016 consultations began between five Kent local authorities (Canterbury, Thanet, Dover, Shepway and Ashford) with a view to forming a new Unitary Authority for East Kent, outside the auspices of Kent County Council.
For almost nine centuries a small part of present-day East London (the
London E16 area), formed part of Kent. The most likely reason for this is that in 1086 Hamon,
dapifer and Sheriff of Kent, owned the manor and, perhaps illegally, annexed it to Kent. It ceased to be considered part of the county in 1965 upon creation of the
London Borough of Newham.