Nephroia carolina, commonly called the Carolina coralbead, snailseed, Carolina Moonseed, or Margil's Vine, is a perennial vine of the moonseed family (Menispermaceae). It is native to North America, where it is found in northeastern Mexico and in several states in the United States from the Southeast to the Midwest.

The species' common name derives from the appearance of its small, rounded red fruits, and the rough half-moon shape of its seeds.