Italy's number one Sinner produced a dazzling display to outclass a helpless De Minaur 6-3, 6-0 after Matteo Arnaldi outlasted Alexei Popyrin in the first singles clash.
Sinner, the world number four, ended the week with five wins out of five, including a heroic performance in Saturday's semi-final when he beat Novak Djokovic to keep his country alive against Serbia after saving three consecutive match points.
He then went on to beat Djokovic and the Serbian's partner Miomir Kecmanovic in the doubles with teammate Lorenzo Sonego to send Italy to the final against 28-time winners Australia and 24 hours later Sinner delivered the title in style.
Hitting the ball with relentless power from the baseline, the Italian dominated from the moment he broke serve early in the first set and there was nothing De Minaur could do.
Sinner's purple patch lasted until he claimed the winning point on his third match point, sparking celebrations amongst teammates, officials and a noisy Italian contingent inside the Malaga arena that has staged the week's captivating Final Eight.
"It helps a lot to play for the whole team and it's been an incredible feeling for all of us," Sinner said as Italy rejoiced at a first Davis Cup title since 1976 and only second ever.
"Thanks to the Australian team for coming all the way here."
'HISTORIC RESULT'
Italian Prime Minister Giorgia Meloni celebrated on the social media platform X.
"A historic result ... congratulations to our players for the talent and commitment they have shown, and also to all the staff," she posted.
Arnaldi was recalled to Italy's singles lineup after missing the semi against Serbia and repaid captain Filippo Volandri's faith by defeating Popyrin 7-5, 2-6, 6-4 in the first singles.
With Sinner in the form of his life, having reached last week's ATP Finals title match which he lost to Djokovic, it was always a tall order after that for Australia, especially as De Minaur had lost to Sinner in all five of their previous matches.
Initially it was tight as De Minaur dug in but Sinner's superior firepower soon earned him a service break and from that point on the outcome looked inevitable.
"Jannik is riding this amazing wave of confidence," De Minaur said.
"He's playing in indoor conditions with some heavy balls where he can hit the absolute crap out of it.
"Today I just didn't have enough."
Lleyton Hewitt's Australia have now been beaten in the final in successive years having lost to Canada in 2022.
Italy and Australia qualify automatically for the 16-nation Finals next year across four cities with the ITF announcing on Sunday that the Final Eight will again be hosted in Malaga.
