Fenestraja plutonia is a species of cartilaginous fish in the family Gurgesiellidae. It is commonly known as the underworld windowskate or the Pluto pygmy skate. The underworld windowskate is known from patches of continental slope in the western Atlantic Ocean between the coasts of the southern United States and Suriname.

Etymology The underworld windowskate's genus name, Fenestraja, comes from a combination of two words. Fenestre is a Latin word meaning window, which in this case refers to a small opening in bone. A second Latin word, Raja simply refers to the genus as a skate/ray of the family Rajidae. Its species name is a reference to Pluto (Ancient Greek: Πλούτων, Ploutōn) the Greek god of the underworld.

The underworld windowskate was initially described by Samuel Garman in 1881 as Raja plutoni. Garman also considered placing the species in other genera such as Breviraja and Gurgesiella. The first specimens had been caught during dredging of the Atlantic coast during the summer of the previous year.