Merced police officers were called out to G Street and Donna Avenue around 5:20 am.
They found the woman lying in the southbound lane of G Street, suffering from moderate to major injuries. She was taken to the hospital, and her current condition has not been released.
Investigators say the driver of the vehicle remained at the scene and is cooperating with officers.
The cause of the collision has not been determined, but police say they do not believe drugs or alcohol were factors.
Officials will have G Street, south of Donna Avenue, closed for a few hours as they continue their investigation.