Sanpoku (山北町 Sampoku-machi) was a town located in Iwafune District, Niigata, Japan.
On April 1, 2008 Sanpoku, along with the town of Arakawa, and the villages of Asahi and Kamihayashi, all from Iwafune District, was merged into the city of Murakami.
As of 2005, the town had an estimated population of 7,243 and a density of 25.95 persons per km². The total area was 283.91 km². It is an isolated town in the northernmost part of Niigata prefecture, connected by the Uetsu Line (JR East) and National Route 7.
Neighboring municipalities are Tsuruoka in Yamagata Prefecture to the north, as well as Murakami and Asahi in Niigata to the south.
The official town tree is the Sugi and the official town flower is the Japanese Lily.