The city of Osan-si is located in the southwestern area of Gyeonggi-do, bordering Hwaseongsi to the east, west, and north, and Pyeongtaek-si to the south. The entire area covers an area of 42.76 ㎢, with a population of about 208,600 (as of January 2015), and is divided into six areas called dongs. The county office is situated in Osan-dong.
* Nature
It is nestled at the end of the Gwangjusanmaek Mountain Range, which originates in the Taebaeksanmaek Mountain Range. Other large hills, all of which are under 200 meters above sea level, are scattered throughout the area, such as Yangsanbong Peak, Yeogyesan Mountain, and Nojeokbong Peak. Osancheon Stream and Hwanggujicheon Stream flow from the east and west into Asanho Lake, respectively.
* Culture
Folk: Osan-si holds the Yutnori (Korean board game) Contest taken place at the Osan Ssalsijang Gwangjang (plaza) from January 8 to 14 on the Lunar Calendar. Only residents of Osan-si may compete.
Dongje (ancestral ritual): Sansinje (religious ritual for the mountain spirit) is held in Naesammi-dong on September 30 at around 9:00 at Pilbong Peak.