下野國
was a feudal domain under the Tokugawa shogunate of Edo period Japan, located in the Nasu region of northern Shimotsuke Province (modern-day Tochigi Prefecture), Japan. It was centered on Karasuyama Castle in what is now part of the city of Karasuyama, Tochigi. Karasuyama was ruled by a number of clans in its early history, but was ruled by a junior branch of the Ōkubo clan from the mid-Edo period onwards. The Karasuyama Ōkubo clan maintained a secondary jin'ya in what is now Atsugi, Kanagawa to administer its extensive holdings in Sagami Province.