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.

The Nippō Main Line is a railway line in Kyushu, in southern Japan, operated by Kyushu Railway Company. Also known as the Fukuhoku Nippo Line, The line connects Kokura Station in Kitakyushu, Fukuoka, and Kagoshima Station in Kagoshima via the east coast of Kyushu, passing through the prefectural capitals of Ōita and Miyazaki. A number of Limited Express trains operate along the route, including Limited Express Sonic trains between Hakata and Oita.