Bitter Orange is a name used to refer to several citrus or citrus-like fruit trees. Citrus aurantium ssp. amara is a spiny evergreen tree native to southern Vietnam but widely cultivated. Bitter oranges are also called sour, bigarade or Seville oranges. They are used as grafting stock for citrus trees, in herbal medicine, in marmalade, and in the liqueurs triple sec and curaçao.

Varieties

Bergamot (Citrus bergamia) is sometimes called Citrus aurantium ssp. bergamia.

Citrus myrtifolia is also called Citrus aurantium var. myrtifolia.

Citris limetta is called a bitter orange.

Poncirus trifoliata sometimes called Citrus trifoliata is called bitter orange or hardy orange.