Prunus cerasus (sour cherry, tart cherry, or dwarf cherry) is an Old World species of Prunus in the subgenus Cerasus (cherries). It has two main groups of cultivars: the dark-red Morello cherry and the lighter-red Amarelle cherry. The sour pulp is edible.

The tree is smaller than the sweet cherry (growing to a height of 4–10 m), has twiggy branches, and its crimson-to-near-black cherries are borne upon shorter stalks.

It is closely related to the sweet cherry (Prunus avium), but has a fruit that is more acidic.

Its fruit persists for an average of 17.4 days, and always bears 1 seed per fruit. Fruits average 84.9% water, and their dry weight includes 39.7% carbohydrates and 1.0% lipids.

Prunus cerasus, a tetraploid with 2n=32 chromosomes, is thought to have originated as a natural hybrid between Prunus avium and Prunus fruticosa in the Iranian Plateau or Eastern Europe where the two species come into contact. Prunus fruticosa is believed to have provided its smaller size and sour tasting fruit. The hybrids then stabilized and interbred to form a new, distinct species.

There are two main varieties (groups of cultivars) of the sour cherry: the dark-red Morello cherry and the lighter-red Amarelle cherry.

It is distributed in much of Europe, North Africa and West Asia. There are likely no truly wild occurrences. However, particularly the subspecies acida easily escapes cultivation and is naturalized throughout the growing area.

Cultivated sour cherries were selected from wild specimens of Prunus cerasus from around the Caspian and Black Seas, and were known to the Greeks in 300 BC. They were also used by Persians and the Romans who introduced them into Britain long before the 1st century AD.^{[citation needed]}