The Piaggio P.XII is an Italian 18-cylinder radial aircraft engine developed in the 1930s by Rinaldo Piaggio S.p.A.

The P.XII was two Piaggio P.X engines in tandem, which were versions of the French Gnome-Rhône 9K Mistral made under license, themselves being much modified Gnome-Rhône 9A - a license-built Bristol Jupiter.

The engine was used in some Italian aircraft from 1940 until the end of World War II, especially the Piaggio P.108.

An up-rated version was tested as the Piaggio P.XXII.

Variants of the Piaggio P.XII include: (R - Riduttore - reduction gearing and C - Compressore - supercharged) Data from Aircraft Engines of the World 1945.