Cyanidin is a natural organic compound. It is a particular type of anthocyanidin (glycoside version called anthocyanins). It is a pigment found in many red berries including but not limited to grapes, bilberry, blackberry, blueberry, cherry, cranberry, elderberry, hawthorn, loganberry, açai berry and raspberry. It can also be found in other fruits such as apples and plums, and in red cabbage and red onion. It has a characteristic reddish-purple color, though this can change with pH; solutions of the compound are red at pH < 3, violet at pH 7-8, and blue at pH > 11. In certain fruits, the highest concentrations of cyanidin are found in the seeds and skin.

Cyanidin, like other anthocyanidins, has putative antioxidant and radical-scavenging effects which may protect cells from oxidative damage and reduce risk of cardiovascular diseases and cancer. Other studies have indicated that dietary intake of cyanidins may inhibit development of obesity by inhibiting the effects of unhealthy diets. Other studies have indicated that cyanidin intake may inhibit development of diabetes as well as provide anti-inflammatory effects.

Other preliminary studies indicate that the glucoside derivative of cyanidin might have a role in cancer therapy, although this remains unproven beyond laboratory testing.