Nakatsu (中津市, Nakatsu-shi) is a city on the northern border of Ōita Prefecture in Kyushu, Japan. The city is on the border with Fukuoka Prefecture. Nakatsu was founded on April 20, 1929. As of March 2017, the city has an estimated population of 84,701 and a population density of 170 people per km2. The total area is 491.09 km2.