Italy won the Davis Cup for the first time since 1976 as Jannik Sinner crushed Alex de Minaur 6-3, 6-0 to seal a 2-0 win over Australia on Sunday in Malaga.

The world number four clinched victory in the second singles rubber after Matteo Arnaldi dug deep to beat Alexei Popyrin 7-5, 2-6, 6-4 in the opening clash.

Sinner, who remarkably beat top-ranked superstar Novak Djokovic twice in one day on Saturday as Italy eliminated Serbia, secured his country's second title against Lleyton Hewitt's 28-time winners in style.

"I felt quite good today ... this is a really important win for me, the whole team and Italy together," said Sinner.

"This is something different, really special, because you don't play for yourself, you play for the whole team."

The Italian demoralised the scampering De Minaur with a relentless performance, overpowering him with vicious ground-strokes to the delight of the majority of the packed Martin Carpena arena.

Sinner had won each of the five prior meetings between the pair and the world number 12 came no closer this time, brutally dismantled in 81 minutes.

Australia's wait for a Davis Cup trophy goes on, with their last coming in 2003, but Italy, who last reached a final in 1998, celebrated wildly when De Minaur went wide to end the tie.

On Saturday Italy were on the verge of elimination, but Sinner saved three match points against Djokovic to force a deciding doubles clash.

"Yesterday we were one point away from being out and now we can celebrate winning, I think we can all be very, very happy," said Sinner, after ending Italy's 47-year wait, the third-longest gap between titles in Davis Cup history.

Sinner, who lost the ATP Finals showdown with Djokovic a week ago in Turin, deserves special credit for his stunning displays in Malaga -- he won all five rubbers he played in.

Laser-focused from the start, he broke early in the first set for a 2-1 lead when De Minaur sent a lob long and then consolidated with a powerful forehand.

The 22-year-old brought up three set points and clinched the first set with the second of them when De Minaur volleyed beyond the baseline.

In the second set Sinner produced 19 winners to just five unforced errors to sweep to victory.

"I will find ways to get better, to be able to hurt these types of players," said De Minaur, who also suffered disappointment with Australia in last year's final.

"Today I just didn't have enough."

- Clinging on -

Arnaldi had to cling on to beat Popyrin in the first match.

"I think I won one of the most important matches in my life, I don't know what to say right now," said an emotional Arnaldi.

"I'm sorry for Alexei, because he deserved to win, for sure -- he was playing better, but sometimes Davis is like this."

Arnaldi, ranked 44th, exchanged breaks with Popyrin and converted his fourth set point to take a scrappy first stanza.

The Australian hit back strongly in the second, racing into a double break and holding for 4-0.

Arnaldi finally got on the board in the fifth game but Popyrin -- who produced six aces in the second set to the Italian's zero -- served it out to force a decisive third.

The erratic Arnaldi saved break points in his first, second and fourth service games without putting pressure on Popyrin's serve until earning a break point which the 24-year-old saved, holding for 4-4.

Popyrin was on top but could not make it count to get the breakthrough, with Arnaldi saving yet another break point on his way to a 5-4 lead.

Despite being outplayed for the best part of the third set Arnaldi converted his first set point to put Italy ahead in the tie with a powerful forehand, with Sinner completing the job without a fuss.

"(Sinner) backed up what he did yesterday against Novak and played extremely good tennis," said Hewitt, who played for Australia last time they won the cup 20 years ago.

"I think the conditions and surface suit him perfectly, as well, which makes life pretty tough."

Victory completed a superb year for Italian tennis, after their women's team finished as runners-up in the Billie Jean King Cup.