Officers responded at 10:46 p.m. to the area of Treat Boulevard and Wilmore Drive on a report of a person lying in the roadway.
Investigators determined the pedestrian was crossing Treat Boulevard between Wilmore and San Simeon drives, an area without a crosswalk, when a vehicle traveling east on Treat struck her, police said.
The woman, whose name is not yet being released by the Contra Costa County coroner's office, was pronounced dead at the scene.
The driver, a 58-year-old Concord woman, initially left the scene but later contacted police and is cooperating with the investigation. The vehicle that hit the pedestrian has been identified as a 2015 Honda, according to police.
Drugs and alcohol do not appear to be factors in the collision.
Treat Boulevard was closed for about five hours during the police investigation. Anyone with information about the case or who witnessed the collision is asked to contact Cpl. Adam Hart at (925) 671-5065.