Koumi is a town located in Nagano Prefecture, Japan. As of 1 April 2019, the town had an estimated population of 4,676 in 2012 households, and a population density of 41 persons per km2. The total area of the town is 114.20 square kilometres. The town mascot is "Ptylitza", an imaginary small gnome-like creature, images of which can be seen all over the town.