The 22-year-old Barcelona midfielder has been regularly linked with a move to Old Trafford and saw his considerable stock rise further as Spain stylishly disposed of the country of his birth.
Alcantara, part of the Spain side that won the tournament in Denmark two years ago, headed home his first after just six minutes, but Italy were quickly level through a fine Ciro Immobile goal.
|Shujaa wa Hat-trick: Thiago Alcantara alipiga bao 3 peke yake katika ushindi wa 4-2|
Manchester City target Isco added to Alcantara's treble in the second half and, despite a nervy ending following a strike from Liverpool's Fabio Borini, but La Rojita retained their title in style.
Spain dominated from the outset and took an early lead through Alcantara, who headed home an Alvaro Morata cross from close range.
It was an impressive goal but one that was soon cancelled out as Giulio Donati played a wonderfully-weighted ball from the back, which Immobile controlled before dinking over Manchester United goalkeeper David de Gea.
Spain quickly returned to the attack and goalkeeper Francesco Bardi had to be alert to deny Morata after the Real Madrid striker was put through by Alcantara.
The Inter Milan goalkeeper was again called into action soon after to stop Koke flicking home a Cristian Tello cross.