Islam in Mongolia is mainly practised by the Kazakhs of Bayan-Ölgii (88.7% of total aimag population) and Khovd (11.5% of total aimag population) aimag in western Mongolia. Some small Kazakh communities are in various cities and towns. The notable community is in the national capital Ulan Bator (Nalaikh düüreg), Töv and Selenge aimags and Darkhan city.

Muslim ethnic groups of Mongolia[1] national censuses data
1956	%	1963	%	1969	%	1979	%	1989	%	2000	%	2007[2]	%
36,729	4.34	47,735	4.69	62,812	5.29	84,305	5.48	120,506	6.06	102,983	4.35	140,152	5.39

High natural increase level caused constant Muslim total population and share growth in 1956-1989. Muslim population declined^[3][4] in 1990-1993 due the ethnic Kazakhs massive repatriation to Kazakhstan.

History

Ghazan's coin were minted with the Islamic declaration of faith When the Mongol Empire broke up into four khanates, three of the four khanates became Muslim.[5] These were the Golden Horde, Hulagu's Ulus and Chagatai's Ulus. The Yuan Empire also embraced Muslim peoples such as the Uyghurs.

Although the court of the Yuan Empire adopted Tibetan Buddhism as the official religion, the majority of the ordinary Mongols, especially those who continued living in Mongolia proper, remained Shamanists. After the decline of the Yuan Dynasty, Shamanism once again became the dominant religion. To varying degrees, political and economic relations with Muslim nations such as Mughalistan and the Uyghurs continued.

The Muslim Kazakhs began to settle in Jungaria and Altai regions since the late nineteenth century. The majority of these Kazakhs were the Kerei and Naiman clans, many of them escaping the persecution of the Czarist Russia. When independent Bogdo Khan Mongolia was established on 29 December 1911, the Kazakhs in Xinjian and Altai regions sought patronage of the restored Khanate. The Government of Bogdo Khan admitted them and settled them in the western region of the Mongolia's Kobdo territory.

Bayan-Ölgii aimag was established as part of the administrative reforms of the Mongolian People's Republic in 1940. Islam is freely practised in the country since Mongolia became a democracy in 1990.

Source : http://en.wikipedia.org/wiki/Islam_in_Mongolia