The Tarawera Ultramarathon scheduled to be held in two weeks has been cancelled, as has the New Zealand Motocross Championships.
It follows the country moving into the red Covid-19 Protection Framework following the Omicron community outbreak.
Ironman Oceania regional director Amy MacCormack said she and the team were disappointed the ultramarathon event couldn't take place.
She said they worked hard to find options to make the event work under the red setting on the scheduled date of February 12.
"However, due to the size, scale and nature of the event, along with the limited time, the only feasible and socially responsible option is to cancel the event," she said.