Lincolnshire, administrative, geographic, and historic county in eastern England, extending along the North Sea coast from the Humber estuary to The Wash. The administrative, geographic, and historic counties cover slightly different areas. The administrative county comprises seven districts: East Lindsey, West Lindsey, North Kesteven, South Kesteven, South Holland, the borough of Boston, and the city of Lincoln. The geographic county encompasses the entire administrative county as well as the unitary authorities of North East Lincolnshire and North Lincolnshire. The historic county is nearly coterminous with the geographic county, except for a few small areas on the northwestern fringes of the North Lincolnshire unitary authority that belong to the historic county of Yorkshire.
Lincolnshire contains two prominent upland areas, which cross it from north to south. The more westerly, and narrower, is Lincoln Edge, a limestone escarpment rising abruptly on its western side and upon which the city of Lincoln stands. Separated from the Lincoln Edge by a clay lowland are the Wolds, an area of rolling chalk hills. Between the Wolds and the coast lies an area known as the Lincoln Marsh; at its southern end it merges into the low-lying area of the Fens, which surrounds The Wash and has been the scene of drainage and reclamation efforts at least since Roman times.