Police confirmed the man had suffered critical injuries to his upper right thigh.
He had been surfing when the attack took place.
Ambulance crews performed CPR on the man, believed to be aged in his 50s, and a chopper arrived on scene to transport him to hospital.
However, the man died at the scene, NSW Police confirmed.
“Despite the best efforts of paramedics and bystanders at the scene, the man could not be resuscitated,” NSW Ambulance said in a tweet.
Authorities have closed Tuncurry Beach and Forster Main Beach, and are working on identifying the species of the shark involved.
NSW Ambulance Inspector Joshua Smyth praised the actions of others who had been on the beach.
“Bystanders, including a retired paramedic, did a valiant job pulling the patient from the water and commencing CPR before paramedics arrived,” he said.
“These people should be commended for their brave actions.”