thumb|Location of Ōoka in Nagano Prefecture
thumb|former Ōoka village hall
was a village located in Sarashina District, Nagano Prefecture, Japan.
As of 2003, the village had an estimated population of 1,467 and a density of 31.99 persons per km<sup>2</sup>. The total area was 45.86 km<sup>2</sup>.
On January 1, 2005, Ōoka, along with the town of Toyono, and the villages of Togakushi and Kinasa (all from Kamiminochi District), was merged into the expanded city of Nagano.