Australian ultra-marathon legend Cliff Young has died at the age of 81.

Famous for his unique half-run and half-walking running gait, Young shuffled off this mortal coil on Sunday afternoon in Queensland after a long illness.

"He has had a lot of strokes recently, his body was just worn out with age," his 83-year-old sister, Helen Simmons, told AAP.

"It was just old age, he had been very low for the last fortnight, we were expecting it to happen."

Young, who lived most of his life in one of the wettest parts of Australia, Beech Forest in the Victorian Otways, moved to Queensland and had been living at Caloundra until recently, Simmons said.

"He will be cremated in Queensland and a memorial service will be held here in Colac at the Bowling Club," she said.

Speaking on Sky News, ultra marathon runner Pat Farmer said watching Young win the 1983 endurance classic was the inspiration behind his decision to take up the sport.

"I was very aware that Cliffy had been sick. He's been sick off and on for quite a number of years now," Farmer said.

"He's the kind of guy you expect to live forever, he was just a wonderful, wonderful human being, and will certainly be remembered as an ordinary man who achieved extraordinary things and never gave up on his goals.

"I wouldn't have done anything without Cliff Young being the inspiration that he was to me."

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