One of the three traditional parts or administrative subdivisions of the English county of Lincolnshire. It extends south from near the city of Lincoln, to the border with Rutland. To the east is the Parts of Holland, to the north is the Parts of Lindsey. It is pronounced kes-STEVE-en.

With the 1974 reorganization of local government Kesteven ceased to be an administrative unit. There are now two districts called North Kesteven and South Kesteven.

The main town is Grantham, birthplace of Margaret Thatcher. In 1992, after she had been deposed as prime minister, she entered the House of Lords with the title Baroness Thatcher: not Baroness of Kesteven as noded elsewhere. The territorial designation that follows her title is "of Kesteven" but this is not part of her peerage title. In fact there was already a Baron Kesteven of Casewick, pronounced KES-ti-ven: John Trollope (1800-1874) was created first baron in 1868, and the title became extinct in 1915.