Thysania agrippina is a species of moth in the family Erebidae. It was described by Maria Sibylla Merian in her 1705 publication Metamorphosis insectorum Surinamensium, and Pieter Cramer provided the formal description of the species in 1776. The most commonly accepted English name is the white witch. Other common names include the ghost moth, great gray witch and great owlet moth. Thysania agrippina is of interest as a competitor for title of "largest insect". This may be true by the measure of wingspan—a Brazilian specimen with a wingspan of almost 30 cm (12 in) appears to hold the record. The Atlas moth and Hercules moth, however, have greater wing areas. The white witch occurs from Uruguay to Mexico, and appears as a stray as far north as Texas in the U.S. Collection dates shows no discernible pattern with respect to location or season.

Moths are a group of insects that includes all members of the order Lepidoptera that are not butterflies. They were previously classified as suborder Heterocera, but the group is paraphyletic with respect to butterflies and neither subordinate taxon is used in modern classifications. Moths make up the vast majority of the order. There are approximately 160,000 species of moth, many of which have yet to be described. Most species of moth are nocturnal, although there are also crepuscular and diurnal species.