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

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

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

Lady Wakehurst Drive was closed in both directions for several hours.

The fatality was one of three serious motorcycle accidents in the region over the weekend.

Another man died after his motorcycle crashed into a tree near Nowra on Saturday.

Inspector Susan Horton of Nowra police said the 51-year-old was thrown from his bike after colliding with a tree on Deans Gap Road at Yerriyong.

The rider died at the scene in the Jerrawangala National Park, a NSW Ambulance Service spokesperson said.

He was believed to be riding in a group.

On Sunday afternoon a woman was airlifted to hospital following a serious motorcycle accident at Jamberoo.

The woman, believed to be in her 40s, was transported to Sydney's St George Hospital around 12.30pm after a crash involving her motorbike and a car on Jamberoo Mountain Road.

A NSW Ambulance spokesperson said the woman had a number of serious injuries to her hip, leg and chest but was stable.

Jamberoo Mountain Road was closed in both directions for several hours while emergency services attended.

The road reopened just before 2pm.