The incident happened at around 6pm on Friday when the girl was crossing the road on Slaemuir Avenue, Port Glasgow.
Emergency services took the girl to the Royal Hospital for Sick Children in Glasgow, where she was treated for serious injuries.
Police Scotland’s Sergeant Chris McKay said: “Our officers are currently trying to establish exactly what happened here and are going through CCTV footage.
“The girl had just gotten off a bus on Slaemuir Avenue before the incident happened and therefore there were lots of people in the area at the time.
“We are appealing for anyone who may have witnessed this incident, or who may have dashcam footage from this area of Port Glasgow to get in touch with us.”