Kuromatsunai (黒松内町 Kuromatsunai-chō) is a town located in Suttsu District, Shiribeshi, Hokkaidō, Japan.
As of March 2008, the town has an estimated population of 3,250 and a density of 9.76 persons per km². The total area is 345.47 km².
The town is the northern most area in Japan where the beech tree grows naturally and as such the beech tree has been designated natural treasure.