The adventure racing event, in which All Black great Richie McCaw competed earlier this year, was set for late March next year over a weekend in the Wanaka area.
But organisers pulled the pin just before Christmas.
Organisers contacted all competitors to "regretfully inform you that Red Bull Defiance, due to be held in Wanaka, New Zealand from the 28-29th of March, is postponed for 2020."
Full refunds will be given to all competitors. No reason was given for the cancellation.
Competitors were offered a discounted entry into the Red Bull Defiance event in Australia in August next year. The Wanaka event was still being advertised on websites and no statement was issued to the media about the cancellation.
The event is the brainchild of Wanaka adventure racer Braden Currie and was first run in 2015.
Currie was a mainstay of the event and won it twice with partners. He scaled back his involvement in the past couple of years as he switched his focus to ironman and triathlon.
The event was taken over by 100% Pure Racing and 100 teams competed in the event in January this year.
Chief executive of 100% Pure Racing Warren Bates could not be contacted yesterday.
The event is a mixture of kayaking, mountain biking, abseiling and clay pigeon shooting.
Next year’s event was to also include a solo category along with two-person and four-person teams. The four-person team category was introduced in the most recent race.
The decision to cancel and the lack of explanation on why it has been cancelled has disappointed entrants.
Athletes would have been in heavy training at this time of year for the event and would have already booked plane tickets and accommodation.
Paul Dawson said on social media that he had been really looking forward to the event but the cancellation had left a sour taste. He was now left wondering what to do with $1000 worth of flights.
Zoe MacClure said although she did not have the expense of flights and accommodation, she had put plenty of time, training and money into the event.
Competitors were upset the event had been cancelled with no explanation.
Competitors felt that with so much commitment they at least deserved to have the reasons behind the cancellation spelt out.
The event originally took place in January but was shifted to late March this year.
March was said to be better by the organisers as it was free of other events, it was after the Coast to Coast and accommodation was also easier to come by in Wanaka.