Tsu (津藩 Tsu-han?) was a Japanese domain of the Edo period, ruled by the tozama Tōdō clan. It was located in the former Ise Province, now known as Mie Prefecture. The Tsu domain's switch to the side of the Satsuma-Chōshū coalition in 1868 is said to be what tipped the balance in the latter's favor during the Battle of Toba-Fushimi. Excluding the Tokugawa and Matsudaira domains, it was the ninth largest domain in Japan by kokudaka.