The Ōmizo Domain (大溝藩 Ōmizo-han) was a Japanese domain of the Edo period, located in Ōmizo, Ōmi Province (modern-day Takashima city, Shiga Prefecture). It was ruled for the entirety of its history by the Wakebe clan. The last lord, Mitsunori, is considered by some to be the very last surviving daimyo, as he died after Hayashi Tadataka; however, Mitsunori became family head as an infant, and in the short interval when daimyo had already lost their titles and been made han chiji (藩知事), or "domainal governors." Therefore, the last individual to have actually been a daimyo in the historic sense was Hayashi Tadataka.