Rhetus is a Neotropical metalmark butterfly genus. They are small (wingspan 25–30 mm), fast flying, strikingly iridescent, and have long wing tails. They are found in open areas, including tracks of primary rainforest. The genus was erected by William John Swainson in 1829. In older literature, all three species were placed in the genus Diorina Morisse 1838 currently viewed as a subjective junior synonym, the older name having priority. Rhetus periander often features in butterfly wall displays.