下野国
was a feudal domain under the Tokugawa shogunate of Edo period Japan, located in Tsuga District of Shimotsuke Province (modern-day Tochigi Prefecture), Japan. It was centered on Mibu Castle in what is now part of the town of Mibu, Tochigi. Mibu was ruled through much of its history by a branch of the "fudai" Torii clan.