The Napier Dagger was a 24-cylinder H-pattern/H-Block air-cooled aero engine designed by Frank Halford and built by Napier before the Second World War. It was a development of the earlier Napier Rapier. It went had four variants and was used in: Fairey Battle (testbed only); Handley Page Hereford; Hawker Hart; Hawker Hector; and Martin-Baker MB 2.