The 27-year-old Coogee man collapsed at Bondi Beach on the last stretch of the annual run on Sunday.

He was taken to St Vincent's Hospital in a critical condition, a spokesman for the NSW Ambulance Service said. A hospital spokesman confirmed he died a short time later.

A spokesperson for the City2Surf said: “It’s a moment of enormous sadness and our thoughts are with his family and loved ones.”

ABC journalist Anne Barker was covering the run for the national broadcaster and saw the man collapse.

"I turned around and saw him almost crawling, clearly in trouble, but still trying to reach the line. He was barely a metre away," she told the ABC.

"He was very white. Suddenly he just collapsed on the ground, rolled on his side and stopped moving."

She said she was paramedics race to the man, who was unconscious, and place him on a stretcher.

"It was all the more distressing because runners were just streaming past him, so clearly happy to have finished, many unaware of what had happened," Ms Barker said.

More than 80,000 people took part in the 14 kilometre race from the Sydney CBD to Bondi Beach - by way of the infamous "Heartbreak Hill".

Olympian Craig Mottram won the race in a shade under 43 minutes. 

smh.com.au, with AAP