thumb|right|200px|It's old Oi village hall with Oi elementary-school in fujimino-city.
was a town located in Iruma District, Saitama Prefecture, Japan.
As of 2003, the town had an estimated population of 47,276 and a population density of 6,014.76 persons per km<sup>2</sup>. The total area was 7.86 km<sup>2</sup>.
On October 1, 2005, Ōi, along with the city of Kamifukuoka, was merged to create the city of Fujimino.