Privet was originally the name for the European semi-evergreen shrub Ligustrum vulgare, and later also for the more reliably evergreen Ligustrum ovalifolium (Japanese privet), used extensively for privacy hedging (hence "privet", private). The term is now used for all members of the genus Ligustrum, which includes about 50 species of mostly evergreen or semi-evergreen shrubs and small trees, native to Europe, north Africa, Asia and Australasia. They are placed in the olive family.

The flowers are small and fragrant and borne in panicles. They have four curled-back petals and two high stamens with yellow or red anthers, between which is the low pistil; the petals and stamens fall off after the flower is fertilized, leaving the pistil in the calyx tube. Flowering starts after 330 growing degree days. The fruits, borne in clusters, are small purple to black drupes, poisonous for man but readily eaten by many birds. In favorable growing conditions, individual shrubs may produce thousands of fruits.

In the some parts of the world where they are not native, some privet species have become invasive weeds, spreading into wilderness areas and displacing native species. This is particularly a problem in North America, where no species of the genus occurs naturally.