It happened outside the Millford Grange housing development on the A283 in Storrington on Saturday morning.
The woman, who lived locally, was taken to the Royal Sussex County Hospital in Brighton, where she died of her injuries.
The rider of the motorbike, a 67-year-old man from Worthing, suffered minor injuries. The road was closed for several hours after the collision.
A 90-year-old woman has died after she was hit by a motorbike in West Sussex.