Harem (Persian: حرمسرا haramsarā, Arabic: حَرِيمٌ ḥarīm, "a sacred inviolable place; harem; female members of the family") refers to domestic spaces that are reserved for the women of the house in a Muslim family. A harem may house a man's wife or wives, their pre-pubescent male children, unmarried daughters, female domestic servants, and other unmarried female relatives. In harems of the past, slave concubines were also housed in the harem. In former times some harems were guarded by eunuchs who were allowed inside. The structure of the harem and the extent of monogamy or polygamy has varied depending on the family's personalities, socio-economic status, and local customs. Similar institutions have been common in other Mediterranean and Middle Eastern civilizations, especially among royal and upper-class families, and the term is sometimes used in other contexts. In traditional Persian residential architecture the women's quarters were known as andaruni (Persian: اندرونی; meaning inside), and in the Indian subcontinent as zenana (Persian: زنانه).

Although the institution has experienced a sharp decline in the modern era due to a rise in education and economic opportunities for women, as well as the influence of Western culture, the seclusion of women is still practiced in some parts of the world, such as rural Afghanistan and conservative states of the Persian Gulf.

In the West, Orientalist conceptions of the harem as a hidden world of sexual subjugation where numerous women lounged in suggestive poses have influenced many paintings, stage productions, films and literary works. Some earlier European Renaissance paintings dating to the 16th century portray the women of the Ottoman harem as individuals of status and political significance. In many periods of Islamic history, women in the harem exercised various degrees of political power, such as the Sultanate of Women in the Ottoman Empire.