Ironman New Zealand hailed a pair of new champions today as Kiwi multisport ace Braden Currie and rising American star Jocelyn McCauley ended the lengthy reigns of Cameron Brown and Meredith Kessler respectively during two pulsating races in Taupo.

In the men's event, Currie, 31, repelled a late charge from Brown, who was seeking to extend his world record to a 13th Ironman New Zealand crown, to add the iconic title to his bulging CV despite his lack of experience over the distance.

Meanwhile, in the women's race, just two years after turning pro, rising star and mother McCauley celebrated success to derail Kessler's bid for a sixth straight title as a scintillating sub-three hour run propelled the 29-year-old to a thumping victory by more than 12 minutes.

An elated Currie become the fourth Kiwi male to win Ironman New Zealand following Scott Ballance, Brown and Bevan Docherty, who like Currie won on debut.

"To win is amazing and I never expected it. I came here to figure out how to race it for next year and I am not sure if I will be able to race as well as today," said Currie.

"Cam is a legend. He is so amazing, strong, repetitive and consistent and never gives up. I knew I could run fast but didn't know how consistent I would be in the marathon ... I was running scared knowing Cam could keep the same pace the whole time."

Currie, a three-time Coast to Coast winner, has in more recent times focused on Ironman racing. He warmed up for today's outing with an eye-catching repeat victory in December's Ironman 70.3 Taupo event and returned to the city to shred a top-class international field which included three former winners in Brown, Estonia's Marko Albert and Belgian Marko Vanhoenacker, who failed to finish.

The man from Methven was always in contention and climbed out of the swim in fifth just ten seconds down on Albert, the first leg leader.

On the bike he refused to panic, even though Terenzo Bozzone at one stage held a lead of more than six minutes to slash the advantage to a little over two minutes by second transition.

From the early stage of the run it was evident Bozzone - who tried to win from the front as he did with his remarkable 7:51 victory in Ironman Western Australia in December - was struggling and once the South Islander confidently strode to the front around the 8km mark of the marathon it was a lead he did not relinquish.

Brown was the big mover in the second half of the race. The 44-year-old veteran ran the quickest marathon of the day in 2:42:29 - just over a minute outside the run course record - but Wanaka-based Currie would not be denied crossing the line in 8:20:57 to win by a victory margin of 3:33.

"The swim was a struggle. It was the hardest swim here in 19 years," said Brown. "I thought the race was gone on the bike leg - I felt nowhere as strong as I did last year; it was a struggle all day.

"At one stage when I was about 14 minutes behind, I thought it was time to retire; but we managed to peg it back and I just never gave up. Braden held on strong and deserved to win."

Cyril Viennot of France also produced an outstanding run, pairing up with Brown for most of the bike and marathon, to grab the final spot on the podium in 8:25:43.

Bozzone, a four-time runner-up, wilted during the run and finished sixth more than 12-and-a-half minutes behind Currie, and was completely spent on the finish line after his daring escape on the bike.

A blistering run enabled McCauley, as befitting a former gifted US collegiate cross country runner, to claim an emphatic maiden Ironman NZ success with an assured display.

The former amateur World Ironman champion who only turned pro in 2015 showed she is a quick learner, and stayed in the hunt when the vastly more experienced Kessler and in-form Australian Annabel Luxford dominated the swim and the first half of the bike.

McCauley worked hard alongside Christchurch-based Briton Laura Siddall and Dutch athlete Yvonne van Vlerken as the trio caught the leaders. The Texan stamped her authority in the run, producing a race time of 9:09:46, passing Kessler at the 14km mark.

"The day unfolded like it would in my perfect dream, I couldn't have asked for anything better," McCauley said.

"I was up against a world-class field and was running scared - I was terrified out of my mind with Siddall (Laura) the comeback-queen behind me - and Meredith, who is a legend.

"I raced my first pro-race here two years ago, and I remember shyly speaking to Meredith beforehand, who told me I would rise to the occasion and I have kept that with me."

Behind, Siddall produced a strong second half of the race to take a commendable second some 12:06 back with Kessler, the five-time former champion, well short of her best today claiming third in 9:27:18.