The South African rode his RC16 to an astonishing 366.1km/h up the Italian circuit's long main straight, beating the old benchmark by 3.5km/h.
KTM already had a potent engine, which appeared to be at least close to a match for Ducati's ‘Bologna bullets', but the Austrian marque also drew attention to its “new, compact aerodynamic design”.
Either of Mugello or Qatar's Lusail typically see the highest speeds of the season, and it is the former where nine of the top 10 figures in history have now been set.
Maverick Viñales, on an Aprilia RS-GP, is now tied with Martin having achieved a 363.6km/h in Saturday's 11-lapper at Mugello.
Binder's top speed came as he tried to fight back after being forced to serve a Long Lap Penalty for first-corner contact which put Alex Marquez on the floor, with the South African going on to finish 11th.
“[There were] A lot of fast people and overtaking. We achieved what we could and it is now important to see where we can improve for tomorrow's race.
“Brad was unlucky and we don't agree with the penalty decision. Otherwise the 366.1km/h is way better than the old record and I hope this will help us to the podium tomorrow!”
He went unpunished over contact with other Marquez, Marc on the #93 Repsol Honda entry, who got home in seventh.