Sanpoku(山北町,Sampoku-machi) was a town located in Iwafune District, Niigata Prefecture, Japan.
As of 2005, the town had an estimated population of about 7,243 and a density of 25.95 persons per km². The total area was 283.91km².
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 expanded city of Murakami.