The Parts of Kesteven is a traditional subdivision of Lincolnshire, England located in the southwest of the county. The subdivision had long been a separate county administration for Quarter Sessions (or courts held quarterly in the year), as did the other two parts, Lindsey and Holland.
Kesteven ceased to be an administrative county in 1974 when Holland, Lindsey and Kesteven were unified into Lincolnshire.
For more information, see the EN Wikipedia article Kesteven. which includes lists of districts and boroughs making up Kesteven.