Billy Slater and Brett Morris both crossed twice and Cooper Cronk added the other try as the Kangaroos produced a devastating performance to win the trophy for the 10th time in 14 editions.
"It is one of the best team performances I have ever been part of," said Australia captain Cameron Smith, who was sprayed with champagne by his jubilant teammates as he lifted the trophy to the backdrop of fireworks at Old Trafford.
New Zealand forward Sonny Bill Williams was bidding to become the first player to win World Cups in both rugby codes but a subdued performance by the world player of the year was summed up when his pass was intercepted in the lead-up to Australia's final try, a length-of-the-field score finished off by Morris in the 72nd minute.
The Australians finished the tournament without having conceded a try in 404 minutes since their win over England in the opening match five weeks ago. In their five games since then, they shipped only four points in five matches, scoring 244.
For Australia's 30-year-olds Smith, Greg Inglis and Johnathan Thurston, who kicked all seven of his goals, it completes the resumes of three of the modern-day rugby league greats in probably their final World Cup. And it goes a long way to making up for the 2008 final, when New Zealand stunned its fierce rival in Brisbane to claim the sport's biggest prize for the first time.
"Five years is a long time to get another opportunity," Smith said, "but a little bit of that disappointment has been taken away by this win."
This was the heaviest victory in a final, eclipsing Australia's 40-12 victory over the Kiwis in the same stadium in 2000.
"I thought their performance was pretty faultless," New Zealand coach Stephen Kearney said.
Australia hadn't been beaten in three years heading into the match but, crucially, New Zealand had defeated its great rival in three of the last four major finals they had met — in that 2008 World Cup and in the Four Nations in '05 and '10.
It quickly became apparent, though, that there would not be another upset here in a match played in front of 74,468 — a record crowd for an international.
Australia was sharper around the play-the-ball, made big yardage through the forwards and had a kicking game through the man-of-the-match Thurston that tormented New Zealand's defence. The Kiwis weren't helped by the seventh-minute withdrawal of right winger Roger Tuisava-Sheck, who sustained a suspected hairline fracture of his right shin in his first carry. Australia made a raft of incisive attacks down its left channel in Tuisava-Sheck's absence, with two of their tries came down that flank.
A halftime scoreline of 16-2 didn't flatter the Kangaroos. The Kiwis walked off with hands on hips, a punishing first 40 adding to the weariness after that epic semifinal victory over England last weekend.
Thurston and Shaun Johnson kicked goals in the opening 16 minutes before Australia's attack started making serious inroads and Thurston's perfectly judged kick was collected by the leaping Slater — soaring way above Kieran Foran — for the opening try in the 19th.
Slater was passed fit only on Thursday after making a quicker-than-expected recovery from a knee injury and his try double — and Australia's victory — will be particularly sweet for the fullback, whose error gifted Benji Marshall a crucial try in the 2008 final.
Isaac Luke somehow held up Cronk over the line to deny the standoff a try in the 25th, but Cronk had the last laugh five minutes later when he collected Darius Boyd's kick forward following another raid down the left to force himself over the line. Luke's slip, just as Cronk gathered the ball, proved decisive.
Thurston converted again — in the process surpassing countryman Mick Cronin to become the record international point-scorer — and his penalty in the 36th gave the Australians a 14-point lead at the break.
New Zealand really needed to score next to make a game of it but it took less than a minute after the break for Slater to virtually clinch the trophy. Again the Kiwis were exposed on their right, as Thurston set free Darius Boyd, who passed inside for Slater to race over.
Morris was next to cross after finishing a great move by diving to ground Jarryd Hayne's kick forward before crashing into the advertising hoardings behind the short in-goal area.
The same duo combined for the crowning try in the 72nd, Hayne intercepting Williams' hopeful miss-pass and sprinting 60 metres before offloading to Morris, who did the rest.
"Tonight just couldn't have gone any better for us," Smith said.