A prune is a dried plum, most commonly from the European plum (Prunus domestica). Not all plum species or varieties can be dried into prunes. A prune is the firm-fleshed fruit (plum) of Prunus domestica varieties that have a high soluble solids content, and do not ferment during drying. Use of the term "prune" for fresh plums is obsolete except when applied to varieties of plum grown for drying.

Most prunes are freestone cultivars (the pit is easy to remove), whereas most plums grown for fresh consumption are clingstone (the pit is more difficult to remove).

Prunes are 64% carbohydrates, including dietary fiber, 2% protein, a rich source of vitamin K, and a moderate source of B vitamins and dietary minerals. The sorbitol content of dietary fiber likely provides the laxative effect associated with consuming prunes.