Ungnadia is a genus of flowering plants in the family Sapindaceae, containing one species, Ungnadia speciosa, commonly known as the Mexican buckeye. It is native to northern Mexico, as well as Texas and southern New Mexico in the United States. The name honors Austrian ambassador Baron David Ungnad von Sonnegg, son of Andreas Ungnad von Sonnegg, who brought the horse chestnut (Aesculus hippocastanum) to Vienna in 1576, introducing the plant into western Europe.

It differs from the buckeyes in the related genus Aesculus but the seeds and nuts are similar. Another similar related genus is the soapberry (genus Sapindus). Ungnadia seeds are poisonous despite their sweetness, and sometimes used as marbles. The foliage is toxic and rarely browsed by livestock, but bees produce honey from the floral nectar.

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