The Blackthorn, is a large shrub or a small tree of the genus Prunus, botanically Prunus spinosa. Its fruit is called the sloe.

The blackthorn is native to Europe, western Asia, and north Africa. The common name is derived from its dark bark and skin, and from the thorns or spines that it bears.

It is covered in white flowers in early spring, and is often the first flowering tree in the countryside in its native regions. It bears a fruit called the sloe, which is similar to a small damson or plum, suitable for preserves, but too sharp to eat; in rural England so-called sloe gin is made from them, though this is not a true gin but a liqueur. In Navarra, Spain, patxaran is a popular liqueur made with sloes.

The blackthorn is extensively planted for hedging and for cover for game birds. Some forms are grown for ornament and flower. The foliage is sometimes eaten by the larvae of Lepidoptera including Emperor Moth, Common Emerald, November Moth, Pale November Moth, Mottled Pug, Green Pug and Feathered Thorn.