A motorist made the discovery on Angeles Crest Highway about three miles north of the 210 Freeway around 5:45 a.m. Investigators said the highway was expected to be shut in both directions for the entire day.
Police released very little information about the victim, but they confirmed that it was not missing Fox News executive Gavin Smith.
The cause of death is unknown, and authorities would not say how long it appeared the body had been there.
"We can't determine, at this time, what exactly his injuries are. There is some ballistic evidence at the scene," said Los Angeles County Sheriff's Lt. Dave Dolson.
Dolson said it appeared the man was killed at the location, but more investigation is needed to confirm.
Anyone with information is urged to call the Los Angeles County Sheriff's Department Homicide Bureau at (323) 890-5500.