Kilsby is a village and civil parish in the Daventry district of Northamptonshire, England, situated approximately five miles south-east of Rugby and six miles north of Daventry.

The village has a population of 1,221 (2001 census). It gives its name to the Kilsby Tunnel on the West Coast Main Line. The tunnel measures 2,400 yards (2,216m) in length, and was designed and constructed by Robert Stephenson, son of the famous George Stephenson. Together, they invented the early steam-engine "The Rocket".