Gynandromorphism is the phenomenon that occurs when an individual organism possesses both male and female phenotypes due to genetic chimera of sex chromosomes in cells across the body and is most easily recognized in species that display sexual dimorphism.

An individual who displays this characteristic is called a gynandromorph. The term comes from the Greek γυνή (gynē) 'female', ἀνήρ (anēr) 'male', and μορφή (morphē) 'form', and is most commonly documented the field of entomology. The definition of “gynandromorphism” is distinct from both intersexuality and hermaphroditism, although they are sometimes used interchangeably.

Gynandromorphism has been noted in Lepidoptera (butterflies and moths) since the 1700s. It has also been observed in crustaceans, such as lobsters and crabs, in spiders, ticks, flies, locusts, crickets, dragonflies, ants, termites, bees, lizards, snakes, rodents, and birds. Although it can be seen in a variety of species, gynandromorphism is notably uncommon. Reporting depends on ease of detecting the phenomenon (whether a species displays noticeable sexual dimorphism) and how well-studied a region or organism is. For example, up until 2023 gynandromorphism had been reported in more than 40 bird species, but the vast majority of these are from the Palearctic and Nearctic; meanwhile, incidents in species from other regions may go underreported due to lack of data collection.