O-Ie S?d? were noble family disputes within the samurai and aristocratic classes of Japan, particularly during the early Edo period. The most famous is the Date S?d?, which broke out among the Date family in the 1660s-70s.
The Tokugawa shogunate which ruled Japan in the Edo period established itself by subjugating warlords, militant religious groups, and other violent groups; their control was predicated on a forcibly imposed peace. As a result, these sorts of noble house disputes, which often came quite close to erupting into outright battle, and which often took place among the powerful tozama families, posed a serious threat to the stability of the bakuhan political system. These events were thus taken very seriously by the government, but also became very popular tales among the people, and were regarded as being quite interesting and exciting, due to the political and physical conflict involved. A number were related in books, and several were even transformed into plays and performed on the Kabuki or bunraku stage, under the genre known as O-ie-mono or O-Ie Ky?gen.