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 2008, the city has an estimated population of 84,179 and a population density of 171 people per km². The total area is 491.09 km².