Mongoloid (/ˈmɒŋɡəˌlɔɪd/) is an obsolete racial grouping of various peoples indigenous to large parts of Asia, the Americas, and some regions in Europe and Oceania. The term is derived from a now-disproven theory of biological race. In the past, other terms such as "Mongolian race", "yellow", "Asiatic" and "Oriental" have been used as synonyms.

The concept of dividing humans into the Mongoloid, Caucasoid, and Negroid races was introduced in the 1780s by members of the Göttingen school of history. It was further developed by Western scholars in the context of racist ideologies during the age of colonialism. With the rise of modern genetics, the concept of distinct human races in a biological sense has become obsolete. In 2019, the American Association of Biological Anthropologists stated: "The belief in 'races' as natural aspects of human biology, and the structures of inequality (racism) that emerge from such beliefs, are among the most damaging elements in the human experience both today and in the past."

The term Mongoloid has had a second usage referencing people with Down syndrome, now generally regarded as highly offensive. Those affected were often referred to as "Mongoloids" or in terms of "Mongolian idiocy" or "Mongolian imbecility".

Mongolian as a term for race was first introduced in 1785 by Christoph Meiners, a scholar at the then modern Göttingen University. Meiners divided humanity into two races he labeled "Tartar-Caucasians" and "Mongolians", believing the former to be beautiful, the latter to be "weak in body and spirit, bad, and lacking in virtue".

His more influential Göttingen colleague Johann Friedrich Blumenbach borrowed the term Mongolian for his division of humanity into five races in the revised 1795 edition of his De generis humani varietate nativa (On the Natural Variety of Mankind). Although Blumenbach's concept of five races later gave rise to scientific racism, his arguments were basically anti-racist, since he underlined that humankind as a whole forms one single species, and points out that the transition from one race to another is so gradual that the distinctions between the races presented by him are "very arbitrary". In Blumenbach's concept, the Mongolian race comprises the peoples living in Asia east of the Ob River, the Caspian Sea and the Ganges River, with the exception of the Malays, who are considered to be transitional between Caucasian and Ethiopian. Of peoples living outside Asia, he includes the "Eskimos" in northern America and the European Finns, among whom he includes the "Lapps".

Discussions on race among Western scholars during the 19th century took place against the background of the debate between monogenists and polygenists, the former arguing for a single origin of all humankind, the latter holding that each human race had a specific origin. Monogenists based their arguments either on a literal interpretation of the biblical story of Adam and Eve or on secular research. Since polygenism stressed the perceived differences, it was popular among white supremacists, especially slaveholders in the US.

British biologist Thomas Huxley, a strong advocate of Darwinism and a monogenist, presented the views of polygenists in 1865: "[S]ome imagine their assumed species of mankind were created where we find them... the Mongolians from the Orangs".

During the 19th century, diverging opinions were pronounced whether Native Americans or Malays should be included in the grouping which was sometimes called "Mongolian" and sometimes "Mongoloid". For example, D. M. Warren in 1856 used a narrow definition which did not include either the "Malay" or the "American" races, while Huxley (1870) and Alexander Winchell (1881) included both Malays and indigenous Americans. In 1861, Isidore Geoffroy Saint-Hilaire added the Australian as a secondary race (subrace) of the principal race of Mongolian.