OPP say a pedestrian was struck by a pickup truck on Thames Street South in Ingersoll, Ont. around 1:45 p.m. on Tuesday.
Police say the 84-year-old woman was transported to a local hospital with serious injuries.
According to investigators, the pickup was southbound on Thames when it struck the woman, who was walking westbound across the street.
The driver of the pickup remained at the scene and is cooperating with the investigation, police say.
Thames Street South was closed between St. Andrew Street and Charles Street for approximately three hours following the incident.
Anyone who witnessed the collision is asked to contact Oxford County OPP.