The horse and a woman rider fell off the Santa Ana trail around noon.
Officials were able to rescue the woman, who suffered minor injuries, but aiding the horse was a more difficult challenge.
They had to first sedate and blindfold the 1,200-pound animal and then bring in an LA County rescue helicopter to hoist it out of the ravine.
Officials believe the horse was not seriously injured in the fall. It appeared to be able to stand after it was brought safely to flat ground.