Officers were called to Five Oaks Road, Slinfold, at around 11.15pm on Tuesday (December 10) after reports of a crash between a black Honda CBR motorcycle and a blue Fiat Panda.
The motorcyclist - a 24-year-old man from Pulborough - suffered serious injuries and was taken to the Royal Sussex County Hospital in Brighton.
The driver of the car - a 59-year-old woman from Worthing - was uninjured.
A police spokesman said: “Police wish to thank the public for their patience while the road was closed for several hours.
“Anyone who witnessed the incident or who may have dashcam footage of the collision, or either vehicle travelling prior to the collision, is asked to email [email protected] or call 101 quoting Operation Duxford.”