Ambulance NSW Illawarra district officer Inspector Terry Morrow said the man was killed instantly after his car hit a tree.

Police said the crash happened just before 7.30am, with emergency services called to Lady Wakehurst Drive following reports a black Mazda 3 had crashed into a tree.

There were no passengers, but the crash was witnessed by a young female cyclist. She was "shaken" but not injured, Insp Morrow said.

At 9.45am the man remained in the vehicle as emergency service crews waited for police rescue and crash investigators to arrive. A crime scene was established.

The road was closed in both directions for several hours, with diversions for southbound along Sir Bertram Stevens Drive and McKell Avenue and for northbound traffic along Lawrence Hargrave Drive and the Princes Highway.

Just after 1pm all lanes were re-opened.