Tsu (津市; -shi) is the capital of Mie prefecture, Japan. It is located on Ise Bay.
As of 2003, the city has an estimated population of 164,214 and the density of 1,612.15 persons per km². The total area is 101.86 km².
Tsu originally developed as a castle town. During the Edo era, it became a popular stopping point for travelers to Ise Shrine, about 40 km to the southeast. The modern city was founded on April 1, 1889. About half of it was destroyed during the American bombing raids of 1945, although it has been rebuilt since then and remains one of the region's principal cities.
Tsu is located on the Kii Main Line, Kintetsu Nagoya Line, and Ise Railway. The closest airport is Nagoya Airport, about 60 km to the northeast.
"Tsu" is believed by many to be the shortest-pronouncable city name in the world.