The Yuba County Five were a group of young men from Yuba City, California, United States, each with mild intellectual disabilities or psychiatric conditions, who attended a college basketball game at California State University, Chico (Chico State), on the night of February 24, 1978. Four of them—Bill Sterling, 29; Jack Huett, 24; Ted Weiher, 32; and Jack Madruga, 30—were later found dead; the fifth, Gary Mathias, 25, has never been found.

Several days after their initial disappearance, the group's car, a Mercury Montego, was found abandoned in a remote area of Plumas National Forest, on a high mountain dirt road that was far out of their way back to Yuba City. Investigators could not determine why the car was abandoned, as it was in good working order and could easily have been pushed out of the snowpack it was in. At that time, no trace of the men was found.

After the snow melted in June 1978, four of the men's bodies were found in and near a trailer camp used by backpackers as shelter, deep in the forest, 20 miles (32 km) from the car. Only bones were left of the three bodies in the woods, a result of scavenging animals; but the one in the trailer, Ted Weiher, had apparently lived for as long as three months after the men were last seen, starving to death despite an ample supply of food and heating materials nearby. Weiher was missing his shoes; investigators found Mathias' own shoes in the nearby woods, suggesting Mathias also survived for some time beyond the group's last sighting.

A local man later came forward, claiming that he had spent the same night in his own car a short distance away from where the Montego was found. The witness told police that he had seen and heard people around his car that night, and twice called for help, only for them to grow silent and turn off their flashlights. This, and the considerable distance from the car to where the bodies were found, has led to suspicions of foul play.