Onishi (鬼石町 Onishi-machi ) was a town located in Tano District, Gunma, Japan.
On January 1, 2006 Onishi was merged into the expanded city of Fujioka.
As of 2003, the town had an estimated population of 6,982 and a density of 133.12 persons per km². The total area was 52.45 km².