The man, believed to be aged 38, suffered a cardiac arrest after his motorbike sped into a tree on Lady Wakehurst Drive, just south of Otford Railway Station, at around 1.30pm.

Paramedics transported the man to Bald Hill where they tried to revive him but he died at the scene.

"We bought in a helicopter to airlift him but the injuries were too serious and he passed away," Wollongong ambulance duty operations manager Norm Rees said.

Lady Wakehurst Drive remains closed in both directions and is expected to be shut for some time.

Motorists leaving the Royal National Park are advised to use either Farnell Ave or McKell Ave.