The Martin family of Portland, Oregon, United States, disappeared on December 7, 1958, in the Columbia River Gorge during a day trip to gather greenery for Christmas decorations. The missing included the husband, Kenneth Martin (aged 54); his wife, Barbara (48); and the couple's three daughters, Barbara ("Barbie"), Virginia and Susan (aged 14, 13, and 11, respectively). The family's eldest child, Donald, was in the United States Navy and stationed in New York State at the time of the disappearance. Several months after the family vanished, the bodies of Susan and Virginia were discovered downstream on the shores of the Columbia River, roughly 30 miles (48 km) apart from each other.

Police initially speculated that the family's car may have crashed into the river, though the circumstances surrounding the event could not be fully explained. Complicating the case was the discovery of a stolen handgun and the arrest of two ex-convicts in the area the day after the family's disappearance. Investigators were unable to determine if the incidents were in any way connected.

The whereabouts of Kenneth, Barbara and Barbie remain undetermined. Their vehicle was possibly discovered in 2024. The family's disappearance has been described as one of the "most baffling" mysteries in Oregon history, and it sparked the greatest manhunt the state had undertaken at the time.