Ethnic Mongols account for about 85% of the population and consist of Khalkha and other groups, all distinguished primarily by dialects of the Mongol language. Mongol is an Altaic language--from the Altaic Mountains of Central Asia, a language family comprising the Turkic, Tungusic, and Mongolic subfamilies--and is related to Turkic (Uzbek, Turkish, and Kazakh), Korean, and, possibly, Japanese. The Khalkha make up 90% of the ethnic Mongol population. The remaining 10% include Durbet Mongols and others in the north and Dariganga Mongols in the east. Turkic speakers (Kazakhs, Turvins, and Khotans) constitute 7% of Mongolia's population, and the rest are Tungusic-speakers, Chinese, and Russians. Most Russians left the country following the withdrawal of economic aid and collapse of the Soviet Union in 1991.

Traditionally, Tibetan Buddhist Lamaism was the predominant religion. However, it was suppressed under the communist regime until 1990, with only one showcase monastery allowed to remain. Since 1990, as liberalization began, Buddhism has enjoyed a resurgence. About 4 million Mongols live outside Mongolia; about 3.4 million live in China, mainly in the Inner Mongolia Autonomous Region, and some 500,000 live in Russia, primarily in Buryatia and Kalmykia.