Fraxinus, 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 trees, although some subtropical species are evergreen trees. The genus is widespread throughout much of Europe, Asia, and North America.

Oleaceae, also known as the olive family or sometimes the lilac family, is a taxonomic family of flowering shrubs, trees, and a few lianas in the order Lamiales. It presently comprises 28 genera, one of which is recently extinct. The extant genera include Cartrema, which was resurrected in 2012. The number of species in the Oleaceae is variously estimated in a wide range around 700. The flowers are often numerous and highly odoriferous. The family has a subcosmopolitan distribution, ranging from the subarctic to the southernmost parts of Africa, Australia, and South America. Notable members include olive, ash, jasmine, and several popular ornamental plants including privet, forsythia, fringetrees, and lilac.