The history of Lincolnshire spans from early Corieltauvi settlement and Roman urbanisation at Lindum Colonia to mediaeval agricultural wealth and 20th-century industry and aviation. Modern Lincolnshire is derived from the merging of the territory of the ancient Kingdom of Lindsey with that controlled by the Danelaw borough of Stamford. For some time the entire county was called 'Lindsey', and it is recorded as such in the Domesday Book. Later, Lindsey was applied to only the northern core, around Lincoln; it was defined as one of the three 'Parts of Lincolnshire', along with Holland in the southeast and Kesteven in the southwest.

During the High Middle Ages, Lincolnshire prospered through the wool trade, generating vast wealth that funded iconic wool churches and made Boston a principal English port. Early modern turbulence followed, including the 1536 Lincolnshire Rising against the Dissolution of the Monasteries and heavy skirmishing during the First English Civil War. The 18th and 19th centuries brought massive agricultural transformation through the systematic land drainage of the Fens, while the first and second world wars established the county as a primary hub for RAF Bomber Command, earning it the moniker "Bomber County".

When county councils were set up in 1888, Lindsey, Holland, and Kesteven were each authorised to have separate "Part" councils. These survived until 1974, when Holland, Kesteven, and most of Lindsey were merged into Lincolnshire, with the northern part, including Scunthorpe and Grimsby, joining the newly formed non-metropolitan county of Humberside alongside most of the East Riding of Yorkshire.

An additional local government reform in 1996 abolished Humberside, and the areas south of the Humber became the unitary authorities of North Lincolnshire and North East Lincolnshire. These areas rejoined Lincolnshire for ceremonial purposes, such as the Lord-Lieutenancy, though they retain separate policing arrangements under Humberside Police. These two authorities sit within the Yorkshire and the Humber region.

The remaining non-metropolitan districts of Lincolnshire are Boston, East Lindsey, Lincoln, South Holland, South Kesteven, North Kesteven, and West Lindsey, which are part of the East Midlands region.

Stone Age During the Pleistocene epoch, Britain's climate alternated between long periods of extreme cold and relative warmth; at least the last three cold spells lead to glaciation, during which ice moved southwards across England.May (1976), pp. 10–13 Lincolnshire was covered by ice in the Anglian and Wolstonian glacial stages and the eastern parts of the county were glaciated during the Devensian.Membery (1979), p. 1 Palaeolithic hunter-gatherers migrated to Britain at least 800,000 years ago, but evidence of early settlement in the Midlands is sparse, probably due to the ice disrupting remains.May (1976), pp. 22–23 Flint flakes at Kirmington in Lincolnshire have been traced to the Hoxnian interglacial, which fell between the Anglian and Wolstonian stages.May (1976), pp. 14–16 Most of the other lower Palaeolithic finds in Lincolnshire are Acheulian hand-axes, which date from that period onwards.May (1976), p. 20; examples of which are flints found at Atterby Carr and BarlingsMembery (1979), pp. 1–2

During the Ipswichian warm period after the Wolstonian, humans began fashioning Mousterian flint-axes, a specimen of which has been found at Risby Warren, near Scunthorpe in northern Lincolnshire. Finds from the late Devensian have also been uncovered at Scunthorpe and dated to between 12,000 and 8,000 BC.May (1976), pp. 23–28 As the Ice age subsided, Britain's climate shifted from sub-Arctic to temperate.May (1976), p. 29 Humans developed more complex and innovative stone tools in the Mesolithic era, although their economy remained chiefly hunter-gatherer.May (1976), p. 32 The Scunthorpe area may have been a "focus of population" during the Mesolithic. A camp at Willoughton has been excavated, revealing hearths and flints; digging at Sheffield's Hill has revealed microliths, indicating a later settlement date, possibly to the 6th millennium BC, while those found at Risby Warren are even more sophisticated and numerous.May (1976), pp. 32–36 Mesolithic sites have also been uncovered along the southern edge of the Lincolnshire Wolds and between Ancaster and Grantham.May (1976), pp. 36–38

The Neolithic is the last stage of Stone Age culture, defined by the use of polished stone tools, a dependence on domesticated plants and animals and the development of pottery and other crafts. Few early Neolithic settlements have been identified in Lincolnshire; examples include a hollow at Dragonby, pottery and flint at Great Ponton, and pottery found in a later barrow at Walesby.May (1976), pp. 43–45 Long barrows have been discovered in the southern and central Wolds and include the Giants' Hills barrows at Skendleby.May (1976), pp. 45–49 Surface artefacts, mostly late Neolithic flint or other stone tools, are found scattered across the county and especially in the lower Trent Valley and the Lincoln Vale.May (1976), pp. 49–57

Bronze Age Beaker pottery emerged during the late Neolithic and survived into the Bronze Age, which heralded the use of Bronze tools instead of stone. Early beaker remains from around Scunthorpe and in the southern Wolds have been dated to the third millennium BC.May (1976), pp. 61–64 Excavations at Risby Warren have revealed a large amount of Bronze Age beaker pottery from the early 2nd millennium BC, while similar material has been identified around Scunthorpe, the southern Wolds and Ancaster.May (1976), pp. 65–68 Although Lincolnshire was once noted for its prehistoric burial mounds, modern farming has destroyed many of them; surviving beaker barrows include the Bronze Age sites at Tallington, Thoresway, Broughton, Cleethorpes, Willoughby and Stroxton, along with scattered tumuli in the Wolds.May (1976), pp. 68–82; see fig. 39 on p. 76 for a distribution map of certain and possible late Neolithic and Bronze Age barrows Middle to late Bronze Age discoveries include a hoard of swords and spearheads from Appleby, a gold torc from Low Burnham (in the British Museum), and a now lost gold "armlet" from Cuxwold.May (1976), pp. 95–101

Changes in vegetation occurred across Britain between roughly 1300 and 600 BC; in Lincolnshire, drier conditions caused pine trees to grow around the Fen edge, while oak forests were largely replaced with peat bogs or moorland. As a result, older settlements were abandoned and new ones began to emerge, leading to difficulties in identifying Bronze Age settlement and burial sites in the county.May (1976), p. 102 However, late Bronze Age hoards are known and one of them, from Nettleham, is in the British Museum; the hoard of bronzes from Bagmoor Farm, near Scunthorpe, indicates a continental influence on craftsmanship and it is likely that an antennae-pommelled sword from the River Witham was imported from Europe.May (1976), pp. 103–106 A wooden trackway from this era has been found at Brigg in north Lincolnshire, nearby to where a wooden boat has been uncovered and tentatively dated to the mid-1st millennium BC. Dug-out canoes have also been uncovered from the Welland, Nene, Trent and Ancholme valleys and the river Witham.May (1976), pp. 112–116

Iron Age

As iron replaced bronze in tool-making in the Iron Age, the distinctive La Tène culture emerged in Celtic societies around 500 BC.May (1976), p. 123 Little material from the early stages of La Tène has been uncovered in Lincolnshire. Examples include a bronze brooch from Scunthorpe and a bronze scabbard or sheath with remains of an iron sword found in Wisbech, one of the earliest pieces of decorated La Tène metalwork in the British Isles.May (1976), pp. 125–128 A now lost anthropoid-hilted iron dagger in a Bronze sheath with an imp-like pommel probably dated from the 2nd or 1st centuries BC, but the beaten bronze shield dredged from the River Witham remains amongst the "finest and largest surviving La Tène art in Europe".May (1976), p. 130 An early Iron Age farming settlement at Ancaster and salterns at Ingoldmells have been excavated;May (1976), pp. 133–141, 144 forts from this period are also known: Honington Camp, Round Hills at Ingoldsby, Careby Camp, and Yarborough Camp. Despite the comparatively small number and size of forts in Lincolnshire, the archaeologist Jeffrey May suggests that the landscape's suitability for farming and its prominent salt industry may have led to prosperity during the Iron Age.May (1976), p. 143

The more decorative late Iron Age finds include gold torcs from Ulceby, bronze terrets from Owmby and Whaplode, a bronze ornament from Dragonby, a strap link from Caythorpe and a sword and scabbard from the River Witham.May (1976), pp. 156–165 Parts of a war horn were also found in the Witham, but were melted down in the 18th century.May (1976), pp. 166–167 There was an "extensive" Iron Age settlement at Old Sleaford, where over 3,500 fragments of coin moulds have been discovered, the largest such find in Europe; it may have been a tribal centre, but never became a walled town under Roman rule.May (1976), pp. 176–179 The Ancaster-Sleaford region has a high concentration of settlement, which may be due to geographical factors and the presence of two north–south communication lines, Mareham Lane and Jurassic Way. Similarly, the northern Wolds were more densely inhabited; settlements at Kirmington and Dragonby have been excavated, while North Ferriby was a crossing on the Humber connected to the south by High Street.May (1976), pp. 179–182 The earliest coinage in Lincolnshire were gold copies of Gallo-Belgic types, but the distinctive South Ferriby type emerged as the dominant pattern in East Midlands and silver coins became much more common from the 2nd century BC.May (1976), pp. 194–199

The pre-Roman East Midlands were occupied by the Corieltauvi tribe. In his Geography, Ptolemy of Alexandria described Lindum (modern Lincoln) and Ratae (modern Leicester) as the principal towns of the tribe. Whether other groups operated in the county is not clear and it may be that the Catuvellauni controlled parts of southern Lincolnshire. The Roman arrival in AD 43 brought the Ninth Legion to the East Midlands to subjugate the native peoples; they may have reached the county by AD 45.May (1976), chap. 8

Roman The Romans established permanent government in Lincolnshire soon after their invasion of AD 43. The tyrannical rule of the Roman sub-prætor Ostorius Scapula so inflamed the Corieltauvi and their neighbours in Yorkshire, the Brigantes, that the two peoples conducted a simmering, low-key rebellion lasting well into AD 70.

Eventually, the Governorship of Britain was given to the Deputy of the Prefect of Gaul, and the title Vicar of Britain created. He resided at York. The sub-district of Flavia Caesariensis, which comprised Lincolnshire and parts of the Midlands, was created.

Once established, the Romans worked to develop infrastructure in Lincolnshire. They built the Car Dyke, a series of semi-natural and artificial boundary ditches which run from the River Welland at Market Deeping for 64 km to the River Witham at Washingborough, constructed hard standings and walkways across the Fens, and also built inland ports, such as the Brayford Pool at Lincoln.

The main Roman forts in Lincolnshire were:

Ancaster Brant Broughton (Briga) Caistor Broughton (Praetorium) Horncastle (Banovalum) Kirton in Lindsey (Inmedio) Lincoln (Lindum Colonia) Louth (Luda) Ludford Stow (Sidnacester) Tattershall (Drurobrivis) Torksey (Tiovulfingacester) Wainfleet (Vainona) Willoughby (Verometum) Winteringham (Ad Abum)

The Romans built three main roads through Lincolnshire: Ermine Street (London to York via Stamford, Lincoln and Winteringham) Fosse Way (Lincoln to Exeter) Tillbridge Lane (Lincoln to York via Marton and Littleborough)