Mukhannath (مُخَنَّث; plural mukhannathun (مُخَنَّثون); "effeminate ones", "ones who resemble women") was a term used in Classical Arabic and Islamic literature to describe effeminate men or people with ambiguous sexual characteristics, who appeared feminine and functioned sexually or socially in roles typically carried out by women. Mukhannathun, especially those in the city of Medina, are mentioned throughout the ḥadīth literature and in the works of many early Arabic and Muslim writers. The historical role and gender identity of mukhannathun have been interpreted by predominantly Western academics of gender studies, Islamic studies, and social sciences as an ancient antecendent to the concept of transgender women in pre-modern Islamic societies.

During the Rashidun era and first half of the Umayyad era, they were strongly associated with music and entertainment. During the Abbasid era, the word itself was used as a descriptor for men employed as dancers, musicians, and/or comedians. In later eras, the term mukhannath was associated with the receptive partner in gay sexual practices, an association that has persisted into the modern day. Khanith is a vernacular Arabic term used in some parts of the Arabian Peninsula to denote the gender role ascribed to males and occasionally intersex people who function sexually, and in some ways socially, as women.

The origins of the term mukhannath in Classical Arabic are disputed. The 8th-century Arab lexicographer al-Khalīl ibn Aḥmad al-Farāhīdī connected the etymology of the term mukhannath to khuntha, meaning "hermaphrodite"/"intersex". According to the 9th-century Arab lexicographer Abū ʿUbayd al-Qāsim ibn Sallām, the term mukhannath instead derives from the Arabic verb khanatha, meaning "to fold back the mouth of a waterskin for drinking", indicating some measure of being languid or delicate. This definition attained prominence among Islamic scholars until medieval times, when the term came to be associated with homosexuality.

Mukhannathun already existed in pre-Islamic Arabia, during the time of the Islamic prophet Muhammad, and early Islamic eras. A number of ḥadīth reports indicate that mukhannathun were used as male servants for wealthy women in the early days of Islam, due to the belief that they were not sexually interested in the female body. These sources do not state that the mukhannathun were homosexual, only that they "lack desire". According to the Iranian social scientist Mehrdad Alipour, "in the premodern period, Muslim societies were aware of five manifestations of gender ambiguity: This can be seen through figures such as the khasi (eunuch), the hijra, the mukhannath, the mamsuh, and the khuntha (hermaphrodite/intersex)."

Gender specialists Aisya Aymanee M. Zaharin and Maria Pallotta-Chiarolli have noted the agreement of scholarly sources on the appearance in the ḥadīth literature of the term mukhannath to mean people who are "obviously male" but carry themselves with femininity in their movements, appearance and vocal characteristics, and on the term's existence as a category distinct from khuntha, intersex individuals who could be either male or female. They also note the contrast between the Arabic term mukhannith, for transgender women that wish to change their biological sex, and mukhannath, which does not carry the same implication.

Various ḥadīth reports state that Muhammad cursed the mukhannathun and their female equivalents, mutarajjilat, and ordered his followers to remove them from their homes. One such incident in the ḥadīth was prompted by a mukhannath servant of Muhammad's wife Umm Salama commenting upon the body of a woman, which may have convinced Muhammad that the mukhannathun were only pretending to have no interest in women, and therefore could not be trusted around them.

Early Islamic historiographical works rarely comment upon the habits of the mukhannathun. It seems there may have been some variance in how "effeminate" they were, though there are indications that some adopted aspects of feminine dress or at least ornamentation. One hadith states that a Muslim mukhannath who had dyed his hands and feet with henna (traditionally a feminine activity) was banished from Medina, but not killed for his behavior. Other ḥadīth also mention the punishment of banishment, both in connection with Umm Salama's servant and a man who worked as a musician. Muhammad described the musician as a mukhannath and threatened to banish him if he did not end his unacceptable career.

In the Rashidun and Umayyad caliphates, various mukhannathun of Medina established themselves as celebrated singers and musicians. One particularly prominent mukhannath, Abū ʿAbd al-Munʿim ʿĪsā ibn ʿAbd Allāh al-Dhāʾib, who had the Arabic name Ṭuways ("Little Peacock"), was born in Medina on the day Muhammad died (8 June 632).