The woman was found around 1:30 p.m. just past mile marker 30 along the Angeles Crest Highway. That's about three miles north of the 210 Freeway and north of La Canada Flintridge.
Los Angeles County Sheriff's Department detectives say the woman was stabbed to death.
Officials are investigating the circumstances of her death.
Anyone with information is asked to contact the Los Angeles County Sheriff's Department Homicide Bureau at (323) 890-5500.
Anonymous information may be provided to Crime Stoppers at (800) 222-TIPS (8477) or by using the website.