Ryōtsu (両津市; -shi) was a city located in Niigata Prefecture, Japan.
In the year 2003, the city had an estimated population of 16,710 and a density of 71.60 persons per km². The total area was 233.37 km².
The city was founded on November 3, 1954. On March 1, 2004 was merged with the rest of Sado Island (the towns of Aikawa, Kanai, Sawata, Hatano, Mano, Hamochi and Ogi, and the villages of Niibo and Akadomari, all from Sado District) to form Sado City.