The double ERC champion started the final stage with a seven-second advantage over Bryan Bouffier, who stopped to change a punctured tyre during the 20.73km Colle d’Oggia test.
Driving a Peugeot 207 Super 2000 on Michelin tyres, Basso’s victory was his second in a row on the legendary asphalt rally.
Meanwhile, ŠKODA Motorsport’s Esapekka Lappi won the stage after "pushing like hell" to beat Alessandro Perico to second place by 4.1s.
Bouffier made it to the finish of the stage but has slipped to fourth overall.
Andreas Aigner secured the ERC Production Car Cup title in his Yokohama-shod Subaru Impreza R4 STI as Federico Gasperetti topped the class in his Renault Mégane R.S. N4.
Daniel Ameglio was leading the ERC 2WD category starting the stage but has stopped in the stage, which hands Alex Vittalini the division spoils.