Acer (pronounced /ˈeɪsər/) is a genus of trees or shrubs commonly known as maple.
Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in Sapindaceae. The type species of the genus is Acer pseudoplatanus (Sycamore maple).
There are approximately 129 species, most of which are native to Asia, with a number also appearing in Europe, northern Africa, and North America. Only one species, the poorly studied Acer laurinum, is native to the Southern Hemisphere. Fifty four species of maples meet the International Union for Conservation of Nature criteria for being under threat of extinction in their native habitat.
The word Acer derives from a Latin word meaning "sharp" (compare "acerbic"), referring to the characteristic points on maple leaves. It was first applied to the genus by the French botanist Joseph Pitton de Tournefort in 1700. The earliest known fossil maple is Acer alaskense, from the Latest Paleocene of Alaska.