|• Revised Romanization||Gilju-gun|
|Province||North Hamgyong Province|
|Administrative divisions||1 ŭp, 5 worker's districts, 22 ri|
The area around Kilju was part of the ancient Goguryeo kingdom and was long inhabited by various Jurchen tribes. In 1107 it was annexed by Goryeo, who gave it its current name (meaning "province of good fortune"). After the ascension of Joseon Dynasty, Kilju was promoted to county in 1398, and in 1509 the county was included in the newly formed Hamgyong Province In 1895, during a reorganization of regional governments, Hamgyong was dissolved and replaced with several small departments; Kilju county was then annexed to the newly formed Kyongsong Department. In 1896 however, the new organization was abandoned, with the departments re-organized into North and South Hamgyong provinces; Kilju was then placed into North Hamgyong, where it remains to this day. During the Japanese occupation, the county was used for manufacturing telecommunications equipment and electric insulation.
Kilju is located in the southern part of North Hamgyong. It borders Myŏngch'ŏn on the east, Kimch'aek and Hwadae to the south, Myŏnggan (Hwasŏng) and Ŏrang to the north. To the west it borders Tanch'ŏn in South Hamgyŏng and Paegam in Ryanggang.
The average annual temperature is 7.5 °C (-7.6 °C in January and 22.2 °C in August).
Tourist sites in Kilju include the former Kilju Magistrate's Hall, built in 1888 to house the office, and the Kilju Hyanggyo, one of the provincial schools founded during the Yi dynasty to teach the children of the rural Yangban (scholar-aristocrats) who lived in the area. ) The Pukkwan Victory Monument, located in this county before the 1950s redistricting, is now located just across the border in what is now Kimchaek city.
In addition to its airport, the county is served by the Pyongra Line railway, which stops at Kilju Chongnyon Station and connects it to Pyongyang and Rason. The city is also linked by road to Hamhung and Chongjin.
Military and nuclear tests
A number of military facilities are known or believed to be located in Kilju. These include the Hwadae-ri atomic weapons training facility. This was first built with Soviet assistance in 1958, and rose to international prominence when the 2006 North Korean nuclear test, the 2009 North Korean nuclear test and the 2013 North Korean nuclear test were reported to have been held at Punggye-ri Nuclear Test Site in the area of Mantapsan mountain, in the northernmost part of the county. The Musudan-ri missile facility is located in nearby Hwadae county, and a separate Scud facility has been reported in the area.
Reports from defectors who lived in the area indicate that residents are suffering from radiation exposure, with high rates of cancers and birth defects being experienced by those living near the Punggye-ri Test Site.
The county is divided into one town (ŭp), five worker's districts (rodongjagu), and 22 villages (ri). 
- Harrison, Bruce (3 December 2017). "'Ghost disease' ravages North Koreans near nuclear site, defectors say". NBC News. Retrieved 2017-12-04.