Versions:
G.91 - light fighter-bomber and reconnaissance aircraft, 4 prototypes and 27 pre-production machines
G.91A - experimental machine for testing slots and tanks in the wings
G.91BS/1 - project derived from G.91T with additional electronic and photographic equipment
G.91BS/2 - project of two-seater version G.91BS/1
G.91E - project of version G.91Y for the Italian Air Force
G.91N - one of the pre-series machines completed with additional navigation equipment
G.91PAN - acrobatic variant for Frecce Tricolori, conversion 20 G.91 and 1 G.91R/1
G.91R - conversion of G.91 to photo-reconnaissance, 4 pcs
G.91R/1 - single-seat variant for the Italian Air Force, three Vinten cameras and four 12.7 mm machine guns; 22 pcs
G.91R/1A - subvariant with equipment version R/3; 25 pcs
G.91R/1B - a subvariant with a reinforced construction, more efficient brakes, tubeless tires and modified instrumentation; 50 pcs
G.91R/2 - variant for the French Air Force, unbuilt
G.91R/3 - variant for the Luftwaffe, better instrumentation, two 30mm cannons, four wing hangers instead of two; 344 pcs
G.91R/3SATS - conversion with JATO auxiliary missiles and catch hook, 1 pc
G.91R/4 - variant for Greece and Turkey, as R/3 but with four machine guns; 50 pcs, taken over by Lufthwaffe
G.91R/5 - proposal for an equivalent R/1 with extended range for Norway
G.91R/6 - variant design with reinforced construction
G.91RS - project derived from G.91A with new wings and Orpheus B.Or 15 engine
G.91T - prototypy dvoumístné training version R/1; 2 pcs
G.91T/1 - serial training variant with two machine guns; 99 pcs
G.91T/2 - draft training version for the French Air Force
G.91T/3 - training variant for the Luftwaffe with R/3 equipment; 66 pcs
G.91T/3 Logair - conversion for data collection
G.91T/4 - variant project for the Italian Air Force with NASARR radar and instruments from F-104
G.91TS - supersonic version project
G.91Y - substantially different twin-engine variant for the Italian Air Force, 2 prototypes and 55 serial
G.91YT - project of two-digit version Y
G.91YS - variant Y for Switzerland, better avionics, possibility to carry Sidewinders; 1 conversion