Ōmiya is one of ten wards of the city of Saitama, in Saitama Prefecture, Japan, and is located in the northeastern part of the city. As of 1 March 2021, the ward had an estimated population of 119,298 and a population density of 9,300 persons per km². Its total area was 12.80 square kilometres (4.94 sq mi). Although Urawa-ku is the governmental center of Saitama City, Ōmiya-ku is the most active commercial and business centre in both Saitama City and Saitama Prefecture thanks to its transport infrastructure, especially railways connected at Ōmiya Station.

Saitama is the capital and largest city of Saitama Prefecture, Japan. Its area incorporates the former cities of Urawa, Ōmiya, Yono and Iwatsuki. It is a city designated by government ordinance. As of 1 February 2021, the city had an estimated population of 1,324,854, and a population density of 6,093 people per km². Its total area is 217.43 square kilometres (83.95 sq mi).