The 55-year-old will begin at Mt Cook and make the journey across to Oamaru in the Alps 2 Ocean Ultra, beginning tomorrow.
Run over seven days, the staged event has attracted 125 competitors from 15 countries.
The first event of its kind in New Zealand, it will be particularly thrilling for Fallon, who has never run a staged ultra before.
She said she had considered travelling to do one, but had stuck to marathons and one-day endurance events in the past.
Now with the opportunity to do one finishing in her home town, she had jumped at the chance.
''Oh gosh, yes. I didn't hesitate at all.
''As soon as [race organiser] Mike [Sandri] told me about it, I said 'yes, I'm in'.
''To be able to do it in your own backyard is fabulous.''
Plenty of preparation had gone into the race, both in the physical sense as well as in preparing logistical things such as what gear she would take.
One of four Oamaru locals competing, she had plenty of support in training and the group was able to keep each other going on their down days.
At 300km long, it was not an easy course.
That meant not running too hard and being aware that you had to be disciplined and what you did on day one could catch up to you on day four or five.
Fallon will be running the course unsupported, meaning she has to carry her own gear, so she has been practising running with weight on her back.
However, in an event that long, it was the mental side of things that were the most important.
''They say that the mental side of it is 90%, really. You've just got to keep yourself up.
''I always break it down - if we're running 55km today, just break it down in 10km lots, because that's roughly where the water stops are.
''Then just break it down to each kilometre; don't think too big, think small.''
It would be the longest race she had done and the next step for her, although she had an impressive CV already.
That included the New York marathon, South Africa's Comrades ultra-marathon, the Naseby 100 mile race, the Kepler Challenge and many marathons around New Zealand.
Having predominantly run marathons, she took up trail running four years ago.
She was ''nearly 56'', although that was not stopping her. She always looked to set herself a goal to have something to strive for.
''I work on the philosophy that if you really want to do something, if you train, you can achieve it.
''You don't have to be a perfectionist at it; it's just live the dream, practise and you'll achieve it if you really want to.
''I think a lot of people are put off because they think 'I can't do it like so and so'.
''You don't have to do it like so and so, because it's you out there doing it.''
More than 60% of the entrants were overseas runners, and there was a 50/50 split between men and women.
