The accident happened at 1.14pm on the A270 Old Shoreham Road at the junction with Lullington Avenue in Hove.
Police say the woman was in collision with a black Toyota Celica and the 39-year-old driver has been arrested for offences.
Emergency services were called to the area and the woman had suffered serious injuries.
She was pronounced dead at the scene.
Her next of kin have been informed.
Police are now appealing for witnesses and anyone who has any information is asked to call 101 and quote Operation Parakeet.