Police said other surfers helped the injured boy ashore. He suffered serious injuries to his leg from the attack and died at the scene despite rescue efforts.
The accident happened at Wooli Beach in New South Wales.
According to the Sydney Morning Herald, the boy was 15 years old. Eyewitnesses said the boy was attacked by white sharks, which are common in the area, the magazine says.
This is the fifth deadly shark attack in Australia this year. A 36-year-old man who was fishing on the east coast of Queensland died in a shark attack last week.
The incidence of shark attacks in Australia is among the highest in the world, but fatal accidents are generally rare.