Matsudaira Katamori was a samurai who lived in Bakumatsu period and the early to mid Meiji period Japan. He was the 9th daimyō of the Aizu Domain and the Kyoto Shugoshoku. He initiated and established the Shinsengumi in 1863. During the Boshin War, he led Aizu Domain against the incipient Meiji government, but was severely defeated at the Battle of Aizu. Katamori's life was spared, and he later became the head kannushi of the Nikkō Tōshō-gū shrine. He, along with his three brothers Matsudaira Sadaaki, Tokugawa Yoshikatsu, and Tokugawa Mochiharu, had highly influential roles during the Meiji restoration and were called the "four Takasu brothers".

Bakumatsu was the final years of the Edo period when the Tokugawa shogunate ended. Between 1853 and 1867, under foreign diplomatic and military pressure, Japan ended its isolationist foreign policy known as sakoku and changed from a feudal Tokugawa shogunate to the modern empire of the Meiji government. The major ideological-political divide during this period was between the pro-imperial nationalists called ishin shishi and the shogunate forces, which included the elite shinsengumi swordsmen.