After restricting unbeaten South Africa to a manageable 8-169 in their semi-final, New Zealand motored to a nine-wicket wicket victory off the back of a remarkable unbeaten century off just 33 balls from Allen -- the quickest ton in the tournament's history -- at Kolkata's Eden Gardens.
Allen, one of the hardest-hitting batters in the white-ball game who helped drive the Perth Scorchers to the BBL title, was at his unstoppable best as he blasted 10 fours and eight sixes while the Black Caps raced into their fourth limited-overs World Cup final on Wednesday (Thursday AEDT).
Though New Zealand won the inaugural World Test crown in 2021, they've previously had no luck in global white-ball finals, losing the 2015 and 2019 50-over showdowns and also the 2021 T20 final.
But they demonstrated once again just how well-equipped they look to finally break their duck as Allen and his opening partner Tim Seifert (58 off 33) led from the front with a dazzling 117-run opening partnership to set up New Zealand's win with 43 balls to spare as they roared to 1-173 with almost contemptuous ease.
With 21 needed, the 26-year-old Allen decided it was time to take down Marco Jansen, hitting the quick-bowling allrounder for 4, 4, 6, 6 and one final glorious thumped off-driven four to reach three figures with the winning blow.
The 24 off that winning over had been preceded by Allen crushing 22 from Corbin Bosch's final over of the power play as he and Seifert bludgeoned 84 off the first six overs.
Seifert actually beat him to his 50, getting there off 28 balls, but Allen needed only 19 balls, the quickest ever against South Africa, to reach his half-century as the pair brought up the 100 partnership in just the eighth over.
Allen, extraordinarily, then just picked up the pace to reel off his second 50 in 14 balls in an innings featuring just three dot balls and 88 runs in boundaries. It beat Chris Gayle's previous record by a whopping 14 balls.
"Someone plays an innings like that, don't think you'll come out on the right side of the result many times as the fielding team," sighed South Africa skipper Aiden Markram. "Massive credit to Finn Allen."
His masterclass came after the Kiwis had earlier stifled the Proteas from the start, once Mitch Santner had inserted them.
Offspinner Cole McConchie (2-9) grabbed wickets in successive balls in his only over, the second of the innings, to remove Quinton de Kock and Ryan Rickelton, while Rachin Ravindra (2-29) helped reduced South Africa to 5-77 before Jansen's unbeaten 55 off 30 balls at least gave them a decent total to defend.
In Sunday's final, Santner's well-drilled crew will play either England or hosts India, who meet in the second semi-final at Mumbai's Wankhede Stadium on Thursday (Friday AEDT) - and the rampaging Allen can't wait.
"You take the positives from this game, celebrate a little moment of success but then we've got a final to win on Sunday -- so we'll look forward to that," he smiled.
FASTEST 100s IN T20 WORLD CUP MATCHES
33 balls - Finn Allen (New Zealand v South Africa 2026)
47 balls - Chris Gayle (West Indies v England 2016)
50 balls - Chris Gayle (West Indies v South Africa 2007)
50 balls - Harry Brook (England v Pakistan 2026)
51 balls - Brendon McCullum (New Zealand v Bangladesh 2012)
