Sumoto is a city situated on Awaji Island within Hyōgo Prefecture, Japan. It occupies the central portion of the island, bordered by the municipalities of Awaji to the north and Minamiawaji to the south. The city lies between the Gulf of Harima on the Seto Inland Sea to the west and Osaka Bay to the east. As an administrative entity, it functions as a local government unit with a mayor-council system and contributes representation to both the prefectural assembly and the national Diet.

The area is located in ancient Awaji Province and developed as a castle town around the Muromachi period with the construction of Sumoto Castle. During the Edo period, it was ruled as part of the Tokushima Domain. Following the Meiji restoration, it became part of Tsuna District before the modern municipal system established the town of Sumoto on April 1, 1889. The settlement was elevated to city status on February 11, 1940, and later expanded through the merger with the town of Goshiki in 2006.

The urban landscape is defined by its historical heritage and natural surroundings, including parts of the Setonaikai National Park. Key landmarks include the ruins of Sumoto Castle, recognized as one of the Continued Top 100 Japanese Castles, and the Yura Fortress. Visitors can explore the Awajishima Historical Museum or the Wellness Park Goshiki Takataya Kahei Park. The city also features the Awajishima Happy Monkey Centre, a notable tourist attraction located within its boundaries.

Cultural appeal is drawn from local traditions and culinary specialties, particularly the production of Awaji onions, Naruto oranges, and Kobe Beef. The economy remains largely rural, supported by agriculture and commercial fishing. Educational infrastructure includes thirteen public elementary schools, five middle schools, and two high schools operated by the prefecture. The city also maintains sister city relationships with Shinhidaka in Hokkaido, Kronstadt in Russia, and counties in Hawaii and Ohio.

As of 1 June 2022, the city had an estimated population of 42,094, with a density of 230 persons per square kilometer across its total area of 182.38 square kilometers. The local economy is based on agriculture and fishing, while transportation relies on the Kobe-Awaji-Naruto Expressway and National Route 28, as there is no passenger rail service. Sumoto experiences a humid subtropical climate with hot summers and cool winters, featuring significant precipitation throughout the year.