Sampson's naiad, Sampson's pearly mussel, or Sampson's riffleshell, scientific name Epioblasma sampsonii, was a species of freshwater mussel in the family Unionidae. It is now extinct. The species was endemic to the United States, where it was found in the drainages of the Ohio River, living in gravel and sand shoals. Like all other members of its genus, its populations declined greatly from early dam and canal construction. The extinction of this species is believed to have occurred sometime in the early 20th century. Little is known about this biology and ecology of this species.