The Napier Rapier was a British 16-cylinder H pattern air-cooled aero engine designed by Frank Halford and built by Napier & Son shortly before World War II.

It was believed that an H pattern engine would provide substantially more power and higher RPM's for the same frontal area as a large liquid-cooled V engine.

The H-block has a compact layout, as it essentially consists of two vertically opposed inline engines lying one beside another driving side by side crankshafts.

The Rapier suffered many of the same problems as the later Dagger and Sabre engines.

The Fairey Seafox and Short S.20 were both powered by the Napier Rapier.