A hermaphrodite is a sexually reproducing organism that produces both male and female gametes

Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic.

The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants.

A rough estimate of the number of hermaphroditic animal species is 65,000, about 5% of all animal species, or 33% excluding insects. Insects are almost exclusively gonochoric. There are no known hermaphroditic species among mammals or birds.