Lancashire is a non-metropolitan county of historic origin in the North West of England. It takes its name from the city of Lancaster (fortress on the Lune - loin - Lonsdale - "far away river"), and is sometimes known as the County of Lancaster.

Although Lancaster is still considered to be the county town, Lancashire County Council is based in Preston. Lancashire is sometimes referred to by the abbreviation Lancs, as originally used by the Royal Mail. The population of the ceremonial county is 1,449,300. People from the county are known as Lancastrians.

The history of Lancashire is thought to have begun with its founding in the 12th century. In the Domesday Book (1086), some of its lands had been treated as part of Yorkshire. The land that lay Inter Ripam et Mersam, "between the Ribble and Mersey", formed part of the returns for Cheshire. Once its initial boundaries were established, it bordered Cumberland, Westmorland, Yorkshire and Cheshire.

Lancashire emerged during the Industrial Revolution as a major commercial and industrial region. The county encompassed several hundred mill towns and collieries. By the 1830s, approximately 85% of all cotton manufactured worldwide was processed in Lancashire. Preston, Bury, Accrington, Blackburn, Bolton, Rochdale, Oldham, Chorley, Darwen, Nelson, Colne, Burnley and Wigan were major cotton mill towns during this time. Blackpool was a major centre for tourism for the inhabitants of Lancashire's mill towns, particularly during wakes week.

The county was subject to a significant boundary reform in 1974, which removed Liverpool and Manchester with most of their surrounding conurbations to form part of the metropolitan counties of Merseyside and Greater Manchester respectively. At this time, the detached northern part of Lancashire in the Lake District, including the Furness Peninsula and Cartmel, was made part of Cumbria. Today the county borders Cumbria, Greater Manchester, Merseyside and North and West Yorkshire. The Duchy of Lancaster exercises the right of the Crown in the area known as the County Palatine of Lancaster, which includes Lancashire as well as parts of Greater Manchester and Merseyside.