The Alvis Leonides Major is a British air-cooled 14-cylinder radial aero engine developed by Alvis from the earlier nine-cylinder Leonides.

[1] In 1951 Alvis started development of a 14-cylinder, two row radial of 1,118 cu in (18.3 L) displacement, based on the Leonides.

The only numerous model of the Major was the Mk.

755/1, a medium supercharged, de-rated, obliquely mounted direct-drive and fan cooled engine fitted to the Westland Whirlwind Mks.

[2] Data from:British Piston Engines and their Aircraft.