A triathlete with a pro cycling background was the top Australian at the world Ironman championships - just not who everyone expected.

Canberra's Ben Hill finished 13th after switching from cycling to triathlon only 12 months ago as the world championships were raced for the first time in Nice, France.

Top Australian Cam Wurf, who also races professionally for British team Ineoc Granadiers, faded on the run and finished a minute behind Hill in 14th place.

Frenchman Sam Laidlow had the biggest win of his career, taking out the 3.8km swim, 180km cycle and 42.2km run event in eight hours six minutes 22 seconds.

He finished nearly four minutes ahead of Germany's two-time Hawaiian Ironman world champion Patrick Lange, with Magnus Ditlev of Denmark taking third and Hill finishing in 8:29:41.

The men's race was moved to Nice because the Ironman world championships had become too big for their traditional home at Kona in Hawaii.

The women's race will go ahead in Kona on October 14 as usual and the two events will swap their locations next year.

Wurf, not surprisingly, had the third-fastest split on the hilly bike course, which featured 2400m of elevation.

But he faded on the flat marathon run, which was four laps of the Promendage des Anglais on the Nice waterfront in warm conditions.

Hill had the seventh-quickest bike leg and then pulled clear of leading triathletes such as German Jan Frodeno, who was in his last Ironman world championship, and Braden Currie of New Zealand, during the marathon.

He had finished only one Ironman triathlon before Nice.

"To overtake Currie straight away and then overtake Frodeno, to be running next to Frodeno, I was just stoked to be on the start line with him, let alone pass him in the run. I know he wasn't on his best day, but that was an amazing feeling," Hill said.

"I'm over the moon, that went absolutely perfectly, I couldn't have dreamed of a better scenario,"

Laidlow finished runner-up at Kona last year to Norwegian star Gustav Iden.

Frodeno finished 24th, but will be remembered as one of triathlon's all-time greats, having won the 2008 Olympic gold medal before three Hawaiian Ironman titles.

The other Australian in the professional field, Nathan Dortmann, did not finish because of injury.

The race featured more than 2000 pro and age-group competitors.