The Imperial Harem of the Ottoman Empire, existing between 1299 and 1923, was the Ottoman sultan's harem composed of the wives, servants (both female slaves and eunuchs), female relatives, and the sultan's concubines, occupying a secluded portion of the Ottoman imperial household. This institution played an important social function within the Ottoman court, and demonstrated considerable political authority in Ottoman affairs, especially during the long period known as the Sultanate of Women. The utmost authority in the Imperial Harem was the Valide Sultan, who ruled over the other women in the household and was often of slave origin herself. The Kizlar Agha (Kizlaragasi, also known as the "Chief Black Eunuch" because of the black African origin of most aghas) was the head of the eunuchs responsible for guarding the Imperial Harem.