Northamptonshire (; abbreviated Northants.) is a county in the East Midlands of England. In 2021, it had a population of 747,622. The county is administered by two unitary authorities: North Northamptonshire and West Northamptonshire. It is nicknamed "The Rose of the Shires".

Covering an area of 2,364 square kilometres (913 sq mi), Northamptonshire is landlocked between eight other counties: Cambridgeshire to the east, Bedfordshire to the south-east, Buckinghamshire to the south, Oxfordshire to the south-west, Warwickshire to the west, Leicestershire and Rutland to the north, and Lincolnshire to the north-east—the last being England's shortest administrative county boundary, at 20 yards (19 metres). Northamptonshire is the southernmost county in the East Midlands.

Apart from the county town of Northampton, other major population centres include Kettering, Corby, Wellingborough, Rushden and Daventry. Northamptonshire's county flower is the cowslip. The Soke of Peterborough falls within the historic boundaries of the county, but its area has been part of the ceremonial county of Cambridgeshire since 1974.