The woman was walking near San Fernando Road and Desmond Street at about 4:35 a.m. Friday. She flagged down a passing driver and asked for help, according to police.
The male driver let her in the car and drove her to the 500 block of 1st Street near San Fernando Recreation Park in San Fernando.
The man then threatened the woman with a knife and raped her, according to police. The suspect left her at the location and drove away.
The suspect was described as a man in his mid-20s, about 5 feet 7 inches tall, with dark brown hair and no facial hair, according to police. He was driving a newer vehicle, possibly a Honda. The color was not determined.
Anyone with information about the rape was asked to call Rosenberg at (818) 898-1261 or (818) 898-1267. Police have video related to the crime.
City News Service contributed to this report.