Musan County is a county in central North Hamgyong province, North Korea. It borders the People's Republic of China to the north, across the Tumen River. It is divided into one ŭp, six , and fifteen ri. The county seat is the town of Musan, Musan ŭp. and are the closest Chinese cities across the river. The land of Musan is high and more than 90% is mountainous and uninhabited; much of it lies on the , while the northwest makes up part of the . The Hamgyong Mountains pass along the county's northwest flank. Musan is the coldest region in North Hamgyong.