The man in his 40s was pulled onto the beach at Byron Bay with a "very serious bite" to his right leg, a spokeswoman for the New South Wales ambulance service was quoted as saying by the Sydney Morning Herald.
Attempts to revive him failed, and he was pronounced dead on the beach, the report said. Part of his leg was later found in the surf.
A two-metre shark was spotted off the same beach not long after the attack.
DPA