Mongolian people; Mongol ethnic group
Refers to the Mongolian ethnic group, often in historical or ethnographic contexts. Not typically used for modern nationality (モンゴル人 is more common).
The Mongolian people are an ethnic group that has lived mainly on the Mongolian Plateau.
From 蒙古 (Mōko, 'Mongolia') + 族 (zoku, 'tribe, ethnic group'). The term 蒙古 is an older Japanese name for Mongolia, derived from Chinese 蒙古 (Měnggǔ).