Ooku

• Japanese: 大奥 (Oo oku)

The Ôoku was the large rear area of the honmaru (main) palace at Edo castle, and was the center of women's residences and activities within the castle. It included the living spaces of the shogun's wives and concubines, their attendants, and other women associated with the castle, and was off-limits to nearly all men, the shogun himself being one of the few exceptions.

In the 1850s, some one thousand women lived in the Ôoku; of them, some 185 were attendants directly in the shogun's service, while the majority of those remaining were attendants in the service of the shogun's mother, wife, or concubines, or female staff hired by the attendants.

The women of the Ôoku maintained a complex hierarchy amongst themselves. The shogun's primary wife, known as midai-sama or midai-dokoro, was at the top of this hierarchy. Others who had given birth to the shogun's children were one rung below the midai, and were known as oheya (lit. "room") as they were entitled to their own private rooms within the palace.