The incident, which was caught on video, happened Thursday evening on Nordhoff Street near Lurline Avenue, according to the Los Angeles Police Department.
Footage shows a gray Ford Focus drifting out of their lane before hitting the skateboarder who was on the right side of the street.
The driver then made a U-turn and took off without helping the victim.
The skateboarder, only identified as a man in his 30s, was taken to the hospital in critical condition.
A reward of up to $25,000 is being offered for information that leads to an arrest. Anybody with information is urged to contact investigators at (818) 644-8025 or (877) 527-3247.
Correction: A previous version of this article stated the incident occurred in Panorama City. This has since been corrected.