Inner Asia refers to the northern and landlocked regions spanning North, Central and East Asia. It includes parts of western and northeast China, as well as southern Siberia. The area overlaps with some definitions of "Central Asia", mostly the historical ones, but certain regions that are often included in Inner Asia, such as Manchuria, are not a part of Central Asia by any of its definitions. Inner Asia may be regarded as the western and northern "frontier" of China proper and as being bounded by East Asia proper, which consists of China proper, Japan and Korea.