Australia was ahead 17-0 after 28 minutes, the tackle count 86-23 against the hosts, as the Black Ferns were initially startled into submission.
Australia was clinical in their breakdown cleanouts, low and strong in their carries and mauled strongly as the Black Ferns were simply starved off the ball.
The opening blow was delivered in the 13th minute when Wallaroos wing Bienne Terita, fended off Black Ferns fullback Renee Holmes and scooted into the right corner.
The Black Ferns burgled the kick-off, but sloppy passing resulted in a spillage collected by Wallaroos left wing Ivania Wong who dashed 65-metres clear.
In the 28th minute the Black Ferns hole became deeper when the illusive Terita found open space on the blindside wing after more ruthless industry from the Wallaroos forwards.
Fire had to be met with fire. At last, the Black Ferns salvaged some possession and a sustained series of pick and goes saw lock Joanah Ngan-Woo emerge underneath a pile of gold bodies.
Australia was suddenly in retreat and when they missed touch from a goal-line clearance they were punished; Portia Woodman crossing out wide after first-five Ruahei Demant drew in two defenders and unloaded.
The Black Ferns were level in the 47th minute when Woodman scored her second. A break by Demant, supported by openside Sarah Hirini saw the Black Ferns storm from 22 to 22. A ruck formed, composure was maintained, and lock Joanah Ngan-Woo fired the last pass.
A horror sequence of events firmly turned momentum in favour of New Zealand. Arabella McKenzie missed a handy penalty from in front 30-metres out in the 52nd minute. A minute later the Black Ferns busted, and Wong was yellow-carded for a deliberate knock-down. Wallaroos skipper Shannon Parry followed Wong on the pine, the pesky openside pinged for unfortunate shoulder on head contact.
Reserve prop Awhina Tangen-Wainohu scored the go-ahead try for the Black Ferns four minutes later by which point Australia were spent.
Woodman completed her hat-trick, combining with fellow Olympic gold-medallist Stacey Fluhler before Women of the match Ruby Tui had the crowd in rapturous, running with unbridled joy as the Black Ferns ambition started to be matched by greater polish.
Remarkably the Black Ferns only trailed at halftime for the second time in a World Cup match. The previous occasion was the 2017 final against England.
Chelsea Bremner made a dozen of her team leading 17 tackles in the first half and alongside Ngan-Woo was the pick of a forward effort that improved throughout.
Australia deserves a lot of acclaim for their heart and start. Loosehead Liz Patu and No.8 Grace Hamilton were exceptional. Lock Atasi Lafai topped the tackle count with 18 and both wings flourished.
In other matches France opened the tournament with a 40-5 victory over South Africa and England thrashed a spirited Fiji 84-19 to extend their winning streak to 26 consecutive Tests and ominously eclipse their previous highest score in a World Cup match which was 82 against Kazakhstan in 2014. England scored 14 tries and meet France next Saturday night in a key Pool C fixture in Whangārei.
The Black Ferns next assignment is against Wales in Waitakere on Sunday. Australia faces Scotland at the same venue.
Rather infamously, before tonight, the largest New Zealand crowd for a women’s sporting event was 16,162 for a Under 17 football World Cup match not involving New Zealand.
Only 45,412 attended the whole World Cup in Ireland in 2017. The previous record for the largest attendance at a women’s rugby international was 20,000. The occasion was the 2014 World Cup final between England and Canada in France.
New Zealand: 41 (Portia Woodman 3, Ruby Tui 2, Joanah Ngan-Woo, Awhina Tangen-Wainohu tries; Renee Holmes 2 con, Kendra Cocksedge con) Australia: 17 (Bienne Terita 2, Ivania Wong tries; Arabella McKenzie con) HT: 12-17