Androgen insensitivity syndrome (AIS), also referred to as androgen resistance syndrome, is a set of disorders of sex development caused by mutations of the gene encoding the androgen receptor (androgen receptor). The set of resulting disorders varies according to the structure and sensitivity of the abnormal receptor. Most forms of AIS involve a variable degree of undervirilization (virilization) and/or infertility in XY (XY sex-determination system) persons of any gender. A person with complete androgen insensitivity syndrome (CAIS) has a female external appearance despite a 46XY karyotype and undescended (Cryptorchidism) testes (testis), a condition once called "testicular feminization" a phrase now considered both derogatory and inaccurate.

Since 1990, major scientific advances have greatly expanded medical understanding and management of the molecular (molecule) mechanisms of the clinical features of AIS. Importantly, advocacy groups for this and other intersex conditions have increased public awareness and spurred acceptance and understanding of the variable nature of gender identity. The value of accurate and scientifically detailed information for patients is now emphasized, with physicians no longer automatically recommending traditional surgical corrections (intersex surgery), with elective option (elective surgery) now viewed as a possible but no longer necessary intervention for ambiguous conditions (ambiguous genitalia).