Ishioka (石岡市, Ishioka-shi?) is a city located in Ibaraki, Japan.
As of February 1, 2011, the city has an estimated population of 79,474, with 29,434 households, and the density of 368.58 persons per km². The total area is 215.62 km².
The city was founded on February 11, 1954.
On October 1, 2005 the town of Yasato, from Niihari District, was merged into Ishioka.