Tsukumi is a city located in Ōita Prefecture, Japan. As of 31 August 2023, the city had an estimated population of 15,492 in 7666 households, and a population density of 190 persons per km2. The total area of the city is 79.48 km2 (30.69 sq mi). Although it has the smallest population among the cities in Ōita Prefecture, it has the third highest population density after Ōita City and Beppu City.

Ōita Prefecture is a prefecture of Japan located on the island of Kyūshū. Ōita Prefecture has a population of 1,136,245 and has a geographic area of 6,340 km2. Ōita Prefecture borders Fukuoka Prefecture to the northwest, Kumamoto Prefecture to the southwest, and Miyazaki Prefecture to the south.