Fraxinus (/ˈfræksɪnəs/), commonly called ash, is a genus of plants in the olive and lilac family, Oleaceae, and comprises 45–65 species of usually medium-to-large trees, most of which are deciduous (dropping their leaves in autumn), although some subtropical species are evergreen. The genus is widespread throughout much of Europe, Asia, and North America.

The leaves are usually opposite, and mostly pinnately compound (divided into leaflets in a feather-like arrangement). The seeds, known as "keys", are botanically fruits of the type called samara. Some species are dioecious, having male and female flowers on separate plants.

Ash wood is strong and elastic, and used for the handles of tools.