Pecco Bagnaia delivered a racing masterclass on home soil, storming into the lead on the second corner and never looking back, building a lead and managing the gap to take a commanding victory.
He was joined on the podium by Enea Bastianini in second and Jorge Martin in third.
Marc Marquez finished fourth, Pedro Acosta fifth, Maverick Vinales eighth and Alex Marquez ninth; all Alpinestars riders.