Sanbongi (三本木町 Sanbongi-chō) was a town located in Shida District, Miyagi, Japan.
On March 31, 2006, Sanbongi was merged with the towns of Iwadeyama and Naruko, both from Tamatsukuri District, the towns of Kashimadai and Matsuyama, all from Shida District, the town of Tajiri, from Tōda District, and the city of Furukawa to create the new city of Ōsaki. Tamatsukuri District and Shida District were dissolved as a result of this merger.
In 2003, the town had an estimated population of 8,405 and a population density of 188.33 persons per km². The total area was 44.63 km².