Lincolnshire () is a ceremonial county in the East Midlands and Yorkshire and the Humber regions of England. It is bordered by the East Riding of Yorkshire across the Humber estuary to the north, the North Sea to the east, Norfolk, Cambridgeshire, Northamptonshire, and Rutland to the south, and Leicestershire, Nottinghamshire, and South Yorkshire to the west.
The county is predominantly rural, with an area of 6,959 km2 (2,687 sq mi) and an estimated population of 1,120,749 in 2024. The port town of Grimsby is in the north-east coast of the county, Boston in the south-east, Grantham in the south-west, the city of Lincoln in the west, and Scunthorpe in the north-west. For local government purposes Lincolnshire comprises a non-metropolitan county, with seven districts, and the unitary authority areas of North Lincolnshire and North East Lincolnshire. The last two areas are part of the Yorkshire and the Humber region, and the rest of the county is in the East Midlands. The non-metropolitan county council and two unitary councils collaborate through the Greater Lincolnshire Combined County Authority.
The county is the second largest in England and has a varied geography. The south-east contains part of the Fens, a naturally marshy region which has been drained for agriculture, and the south-west is an upland region. A wide vale runs north–south from the centre to the north of the county. To its east, the chalk hills of the Lincolnshire Wolds, which have been designated a national landscape, occupy the north-east, with a coastal plain and the Lincolnshire Marsh beyond. The west of the vale is demarcated by the Lincolnshire Edge, a long escarpment; at its northern end are the Coversands, an area of heath. Beyond the edge, the western border of the county contains the eastern part of the Trent Valley and, in the north, part of the Humberhead Levels, with the River Trent itself forming part of the border.
Lincolnshire has had a comparatively quiet history, being a predominantly rural county that was not heavily industrialised and faced relatively limited external threats compared to other regions of England. In the Roman era Lincoln was a major settlement, called Lindum Colonia. In the fifth century what would become the county was settled by the invading Angles, who established the Kingdom of Lindsey in the north of the region. Lincoln became the centre of a diocese in 1072, and Lincoln Cathedral was built over the following centuries. The late Middle Ages were a particularly prosperous period, when wealth from wool trade facilitated the building of the grand wool churches such as St Botolph's Church, Boston. During the Second World War the relatively flat topography of the county made it an important base for the Royal Air Force, which gave rise to the nickname 'Bomber County'.
During pre-Roman times, most of Lincolnshire was inhabited by the Corieltauvi people. The language of the area at that time would have been Common Brittonic, the precursor to modern Welsh, Cornish and Breton. The name Lincoln was derived from Lindum Colonia.
Large numbers of Germanic speakers from continental Europe settled in the region following the withdrawal of the Romans. Though these were later identified as Angles, it is unlikely that they migrated as part of an organised tribal group. Thus, the main language of the region quickly became Old English. However, it is possible that Brittonic continued to be spoken in some communities as late as the eighth century.
Modern-day Lincolnshire is derived from the merging of the territory of the 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 11th-century Domesday Book. Later, the name Lindsey was applied to the northern core, around Lincoln. This emerged as one of the three Parts of Lincolnshire, along with the Parts of Holland in the south-east, and the Parts of Kesteven in the south-west, which each had separate quarter sessions as their county administrations. Lindsey was traditionally split between the North, South and West Ridings of Lindsey.
The area was shaken by 27 February 2008 Lincolnshire earthquake, reaching between 4.7 and 5.3 on the Richter magnitude scale; it was one of the largest earthquakes to affect Britain in recent years.
Lincolnshire is home to Woolsthorpe Manor, birthplace and home of Sir Isaac Newton. He attended The King's School, Grantham. Its library has preserved his signature, carved into a window sill when he was a youth.
The geographical layout of Lincolnshire is quite extensive and mostly separated by many rivers and rolling countryside. The north of the county begins from where the Isle of Axholme is located near the meeting points of the rivers Ouse and Trent near to the Humber. From there, the southside of the Humber estuary forms the border between Lincolnshire and the East Riding of Yorkshire. From there, the south bank of the Humber Estuary where the Humber Bridge crosses the estuary at Barton upon Humber, is used primarily for the shipping ports at Immingham, New Holland and Grimsby. From there, the rest of the southern bank forms the Lincolnshire Coast from Cleethorpes to Mablethorpe and then onto Skegness. From Skegness, the rest of the Lincolnshire Coastline forms the sea boundary and border with Norfolk at the Wash. The coast then at Boston becomes the meeting point of the rivers Welland and Haven in an area known as the "Fosdyke Wash".
The rest of the sea boundary runs from Fosdyke to the east of Sutton Bridge, where the current land boundary with Norfolk is located in a narrow area of reclaimed farmland just to the east of the River Nene, but until as recently as the early 19th century there was no land border between Lincolnshire and Norfolk as it was separated from each other by the "Cross Keys Wash" a former area of estuary and marshland where the River Nene used to flow out into the Wash and could only be crossed at low tide by a causeway or ferry and was the natural boundary between the two counties. The causeway known at the time as the "Wash Way" was renowned as being particularly treacherous and the safer route was to go into Norfolk from Lincolnshire via the Cambridgeshire town of Wisbech and this element remains to the present day as the Cross Keys Bridge at Sutton Bridge provides the only direct access point to Norfolk from Lincolnshire over the River Nene some nine miles north of Wisbech. The border with Lincolnshire to Cambridgeshire begins at Crowland, Market Deeping and Stamford which form the southern boundary of the county with both Peterborough, Rutland and briefly Northamptonshire; the county's border with Northamptonshire is just 20 yards (19 m) long, England's shortest county boundary. From there, the border with Leicestershire and Nottinghamshire begins at Sleaford, Grantham, Lincoln and Gainsborough. From Gainsborough, the border with South Yorkshire begins at Haxey and Epworth before looping back to the original north of the county near Scunthorpe with East Riding of Yorkshire at the Isle of Axholme and Goole.
Bedrock in Lincolnshire features Jurassic limestone (near Lincoln) and Cretaceous chalk (north-east). The area around Woodhall Spa and Kirkby on Bain is dominated by gravel and sand. For much of prehistory, Lincolnshire was under tropical seas, and most fossils found in the county are marine invertebrates. Marine vertebrates have also been found including ichthyosaurus and plesiosaur.
The highest point in Lincolnshire is Wolds Top (168 m, 551 ft), at Normanby le Wold. Some parts of the Fens may be below sea level. The nearest mountains are in Derbyshire.
The biggest rivers in Lincolnshire are the Trent, running northwards from Staffordshire up the western edge of the county to the Humber estuary, and the Witham, which begins in Lincolnshire at South Witham and runs for 132 km (82 miles) through the middle of the county, eventually emptying into the North Sea at The Wash. The Humber estuary, on Lincolnshire's northern border, is also fed by the River Ouse. The Wash is also the mouth of the Welland, the Nene and the Great Ouse.