The Khalkha dialect is a dialect of Mongolian widely spoken in Mongolia and according to some classifications includes such South Mongolian varieties such as Shiliin gol, Ulaanchab and Sönid. As it was the basis for the Cyrillic orthography of Mongolian, it is de facto the national language of Mongolia. The name of the dialect is related to the name of the Khalkha tribe and the Khalkha river. Wikipedia
Mongolia