相馬氏
was a feudal domain under the Tokugawa shogunate of Edo period Japan., based at Iwakitaira Castle in southern Mutsu Province in what is now part of modern-day Iwaki, Fukushima. Its southern neighbor was the Mito Domain which was ruled by the Mito Tokugawa clan, and its northern neighbor was the Nakamura Domain which was ruled by the Sōma clan. The han school was the "Shiseidō" (施政堂), founded by the Andō clan. The most famous culture created in the Iwakitaira Domain is the "Jangara Nembutsu" dance.