The Piaggio P.XI was an Italian 14-cylinder radial aircraft engine.

The P.XI was a licensed derivative of the French Gnome-Rhône Mistral Major 14K produced in Italy.

[1] Further development led to the P.XIX.

This featured an increased compression ratio from 6:1 to 7:1 and an rpm increase from 2,400 to 2,600.

Data from Italian Civil & Military Aircraft 1930-1945 and Aircraft Engines of the World 1945.