Southern Mongolian or Inner Mongolian is a proposed major dialect group within the taxonomy of the Mongolian language. It is assumed by most Inner Mongolian linguists and would be on the same level as the other three major dialect groups Khalkha, Buryat, Oirat. (Within this classificational scheme, Oirat usually includes Kalmyk, but a classification that assumes Kalmyk as a major dialect group of its own right also exists.) Southern Mongolian would consist of the dialects Chakhar, Ordos, Baarin, Khorchin, Kharchin and (possibly) Alasha that originated from Oirat. The varieties spoken in Xilin Gol which form a major dialect of their own right and are close to Khalkha are classified as belonging to Chakhar in this approach. Because Southern Mongolian would consist of all non-Buryat Mongolian varieties spoken in Inner Mongolia, this classification has been argued against by several linguists who hold that there is a dialect continuum between Khalkha and the Southern Mongolian varieties that rather favours grouping Chakhar, Ordos and Khalkha on the one hand and Khorchin and Kharchin on the other hand, or at least that "Mongolian proper" is an immediate member of Mongolian/Mongolic. On the other hand, the argument that Southern Mongolian is distinct is based on considerations such as the following:

• Southern Mongolian is the Standard dialect of Inner Mongolia, while Khalkha is the Standard language of the Mongolian state.
• Southern Mongolians continue to use the Mongolian script, while Khalkhas have switched to Cyrillic script, which rather closely resembles the pronunciation of the Khalkha dialect.
• Southern Mongolian has been under strong influence from Chinese, while Khalkha has been under strong influence from Russian.