Oyama is a city located in Tochigi Prefecture, Japan. As of 1 August 2020, the city had an estimated population of 167,647 in 70,928 households, and a population density of 980 persons per km2. The total area of the city is 171.76 square kilometres (66.32 sq mi). In 2006, Oyama became the second most populous city in Tochigi Prefecture, with the capital Utsunomiya retaining the number one spot.

Tochigi Prefecture is a landlocked prefecture of Japan located in the Kantō region of Honshu. Tochigi Prefecture has a population of 1,897,649 and has a geographic area of 6,408 km². Tochigi Prefecture borders Fukushima Prefecture to the north, Gunma Prefecture to the west, Saitama Prefecture to the south, and Ibaraki Prefecture to the southeast.