A cyclist is in a critical condition in hospital after a crash involving a car near Cronulla in Sydney's south this morning.

Emergency services were called to the scene on Captain Cook Drive, Greenhills Beach, following reports of a crash between a cyclist and a Holden Astra.

It's understood the cyclist, a 63-year-old man, was thrown several metres and suffered significant injuries. He was taken to St George Hospital where he underwent surgery and remains in a critical condition.

The driver, a 72-year-old man from Kurnell, was not injured. He was taken to Sutherland Hospital for mandatory testing.

He was later arrested and taken to Sutherland police station where he was charged with dangerous driving occasioning grievous bodily harm and negligent driving occasioning grievous bodily harm.