A cyclist has been critically injured in a crash with a car near a popular sports ground in Sydney's south, police say.

The 32-year-old man suffered major head and facial injuries in the collision on Holbeach Avenue in Tempe, next to the Tempe Recreation Reserve, on Tuesday night.

Police said the cyclist had been riding on the footpath but, when he joined Holbeach Avenue, he was involved in a collision with a Toyota Camry about 8.50pm.

A NSW Police spokeswoman said the cyclist was wearing a helmet at the time, but he suffered critical head injuries.

He was taken to Royal Prince Alfred Hospital, where he remained in a critical condition on Wednesday morning.