The Ambulance service was called at around 3.15pm on Thursday 1 August, following reports of a single vehicle collision involving a bicycle on Liskey Hill, Perranporth.
Ambulance units including a tri service officer was deployed to the scene together with the air ambulance. The female cyclist sustained a serious injury to her head and was taken to Derriford hospital by air ambulance where she remains in a critical condition.
Police were not notified of the incident until 4.30pm and therefore once the casualty was removed the road remained open. Officers attended and closed the road for further examination; it was reopened at 8pm.
Police are appealing for any witnesses with any information, who have not already been in contact with officers at the scene, to get in touch.
Anyone who witnessed the incident and anyone with information is asked to contact police on 101 quoting log 705 1/8/19.