Eutheria is a classification system nearly synonymous with Placentalia. Introduced by Thomas Henry Huxley in 1880, he meant for it to be more broad in definition than its precursor Placentalia. However, the noun placental is used almost universally to describe a placental mammal; placental mammals are rarely, if ever, referred to as eutheres. As a result, Placentalia remains the preferred choice for many scientists.

See also: Mammal for classification.