The lightning whelk, scientific name Sinistrofulgur perversum, is an edible species of very large predatory sea snail or whelk, a marine gastropod mollusc in the family Busyconidae, the busycon whelks. This species has a left-handed or sinistral shell. It eats mostly bivalves. There has been some disagreement about the correct scientific name for this species, which has been confused with Busycon sinistrum Hollister, 1958, and Busycon contrarium (Conrad, 1840), which is an exclusively fossil species.