A Geraldton woman in her sixties is in a critical condition after she fell from a horse yesterday.

It is believed the woman was wearing a helmet at the time and riding the horse at speed when the accident happened on a Glenfield property.

A Royal Flying Doctor Service spokeswoman said she suffered life-threatening head injuries.

She was taken by ambulance to Geraldton Regional Hospital about 6.50pm and early this morning transferred by Royal Flying Doctor Service to Royal Perth Hospital.

A hospital spokeswoman today said the woman remained in a critical condition.