The street has been closed to all westbound traffic while a number of bus services have been diverted via Randolph Crescent and Queen Street.
A Police Scotland spokeswoman said: “Police Scotland is currently in attendance following a road traffic collision in Princes Street.
“The incident occurred today at around 11.10am when a woman was involved in a collision with a bus.
“She sustained a head injury and has been taken to the Edinburgh Royal Infirmary for treatment by the Scottish Ambulance Service.
“Road closures are currently in place at the West End of Princes Street and Lothian Road.
“Anyone with information regarding this incident is asked to contact Police Scotland on 101.”