The 3000km Te Araroa trail spans the length of the country from North Island's Cape Reinga to Bluff in the South Island.
Karel Sabbe completed it in 31 days, 19 hours and 41 minutes, beating the previous record by over 17-and-a-half days.
Sabbe told RNZ's Morning Report programme today he ran an average of 96kms a day - that's more than two marathons.
"It was a very adventurous trail and was so rewarding to spend so much time in such a beautiful country."
However, the run didn't come without its challenges.
"One moment you can be gently running on a trail and then suddenly it becomes like rough tramping," Sabbe said.
Te Araroa is a diverse trail, winding through high mountain passes, rivers, cities and towns.
"You have so many river crossings, many times that you have to run in streams. So, basically all the time your feet are wet."
A crew of five people helped him along the run, however, an attack by two wild dogs left one of his friends with a broken elbow 400km in.
Sabbe has hiked in many countries, previously having set several speed records for trails around the world.
He holds the record for the Pacific Crest Trail in North America.
