Olympic silver medallist Lisa Norden of Sweden defied food poisoning to win her first women's world championship title.
The 27-year-old discharged herself from hospital on the morning of the final event of the eight-race World Series.
Olympic bronze medalist Erin Densham led the overall standings by 30 points into the Auckland finale, only to withdraw with illness in the cycling.
Anne Haug won the event but Norden's fourth-place finish gave her a total of 4,531 points, 191 above Haug in second.
"I didn't think I was going to be able to start the race today," admitted Norden, who was denied Olympic gold at London 2012 after finishing second to Switzerland's Nicola Spirig in the first ever triathlon photo finish.
"I dug the deepest I've ever dug in my life. It's been an amazing year with lots of ups and downs but if you have enough downs at some stage you're going to get the ups. I'm just so pleased to be part of my own fairytale."
The withdrawal of Densham, who had been troubled by illness for much of the week, left Norden needing to finish in the top six to secure the title.
Haug of Germany broke away from the leading group on the last lap of the 10km, run which followed a 1.5 km swim and 40km cycle leg around Auckland's central business district.
Briton Jodie Stimpson was part of a group of 11 in contention in the closing stages, but eventually finished fifth as Haug recorded her first victory of the series, while New Zealand's Andrea Hewitt, who finished seventh on Saturday, claimed third place overall.
Earlier, Wales' Non Stanford won the women's under-23 race. Stanford is part of the Leeds-based training group that includes the Brownlee brothers.
Jonny Brownlee will attempt to succced his brother Alistair as world champion when he competes in the men's race in the early hours of Sunday morning, British time.
Olympic bronze medallist Brownlee needs a podium finish in Auckland to secure the title, with Spaniard Javier Gomez - silver medallist in London - the only other athlete with a realistic chance of taking the title.
There will be live coverage of the mens race from 1am on Sunday morning on the Red Button. And there will be a highlights programme on BBC2 on Sunday from 14:05 - 16:30 rounding up all the weekend's racing in Auckland.
Women's Grand Final result:
1 Ann Haug, Germany, 2 hours 10 minutes 49 seconds.
2 Gwen Jorgensen, United States, 2:10.59
3 Barbara Riveros Diaz, Chile, 2:11.00
4 Lisa Norden, Sweden, 2:11.03
5 Jodie Stimpson, Britain, 2:11.04
1 Lisa Norden, Sweden, 4531 points
2 Anne Haug, Germany, 4340
3 Andrea Hewitt, New Zealand, 3893
4 Barbara Riveros Diaz, Chile, 3707
5 Erin Densham, Australia, 3611