The scene of the collision in Romford
The pedestrian, who is in her 30s, was rushed to hospital after the crash at the junction of South Street and Western Road.
Emergency Services were called at around 4.25pm this afternoon.
Police say the male bus driver has been arrested on suspicion of dangerous driving.
He is currently in police custody.
The road was closed after the collision but it has since reopened.
Tags: Romford, Havering? CLEARED ? Western Road, RM1: All affected routes are back to normal service following clearance of the earlier collision. https://t.co/eWL53jNSkY
— TfL Bus Alerts (@TfLBusAlerts) February 15, 2020