Saganoseki (佐賀関町 Saganoseki-machi?) was a town located in Kitaamabe District, Ōita Prefecture, Japan.
As of 2003, the town had an estimated population of 12,367 and the density of 250.39 persons per km². The total area was 49.39 km².
On January 1, 2005, Saganoseki, along with the town of Notsuharu (from Kitaamabe District), was merged with the expanded city of Ōita.