Rotorua's Jamie Milne will attempt to run from Bluff to Picton in 12 days to raise awareness for Ronald McDonald House.
The Rotorua born and bred ultra runner will have to average about 80km per day to complete the 922km challenge, the equivalent of two marathons per day.
Mr Milne, who works as Shane Cameron's strength and conditioning coach, will be running solo but will be joined by supporters following him in a vehicle.
Mr Milne and his team want to make a difference for their chosen charity, Ronald McDonald House, and will begin the long journey on December 1.
Ronald McDonald House helps develop and support programmes for children to live happier, healthier lives and also accommodate parents when their children are in hospital.
"Everyone involved with this event has donated their time, energy and enthusiasm to help achieve this incredible feat of physical and mental human endurance," he said.
Mr Milne's journey into ultra-distance running began after leaving the Royal New Zealand Navy in 2002.
A lifestyle of food, alcohol and inactivity saw him go from 74kg to an unhealthy 112kg.
One day, his grandfather remarked "You look disgusting son, you only have yourself to blame".
After the criticism, Mr Milne decided to turn his life around and the very next morning, hung over and embarrassed, he went for a run.
Ten years later he has not stopped. To follow him go to www.kiwiconditioning.co.nz, where you can also donate to the cause.