The Municipality of Hrastnik is a municipality in central Slovenia. The seat of the municipality is the town of Hrastnik. The area is part of the traditional Styria region. The entire municipality is now included in the Central Sava Statistical Region. Located in the valley of a minor left bank tributary of the Sava River, the area is known for its rich deposits of coal. Coal mining began in the area in 1804. Surrounding peaks include Mount Kum, Mount Mrzlica, and Kopitnik Hill.