The PZL.45 Sokół (falcon) was a Polish prototype fighter designed by PZL from 1936–1939.
Work commenced on the aircraft in the late 1936 based on earlier light fighters.
The aircraft had a fixed undercarriage and the aircraft was powered by a Gnome-Rhône 14M05 Mars, a 14-cylinder radial engine with a maximum of 760 hp (567 kW), with a fuel tank holding 350 litres (77 imp gal; 92 US gal).
The design was finished in 1938, and the first model was made in February 1939 with technical documentation completed in June of that year.
The aircraft was also designed to be equipped with 4 machine guns (2 wing-mounted and 2 in the hull), though the prototype was not armed.