D. Napier & Son Limited was a British engineering company best known for its luxury motor cars in the Edwardian era and for its aero engines throughout the early to mid-20th century.

Napier was founded as a precision engineering company in 1808 and for nearly a century produced machinery for the financial, print, and munitions industries. In the early 20th century it moved for a time into internal combustion engines and road vehicles before turning to aero engines. Its powerful Lion dominated the UK market in the 1920s and the Second World War era Sabre produced 3,500 hp (2,600 kW) in its later versions. Many world speed records on land and water, as well as the Hawker Typhoon and Tempest fighter planes, were powered by Napier engines. During the Second World War the company was taken over by English Electric, and engine manufacture eventually ceased. Today, Napier Turbochargers is a subsidiary of the American company Wabtec.