Bitter orange, Seville orange, sour orange, bigarade orange, or marmalade orange refers to a citrus tree (Citrus aurantium) and its fruit. It is native to Southeast Asia, and has been spread by humans to many parts of the world.
Wild trees are found near small streams in generally secluded and wooded parts of Florida and The Bahamas after it was introduced to the area from Spain where it had been introduced and cultivated heavily at the beginning in the 10th century.
It is a hybrid between Citrus maxima (pomelo) and Citrus reticulata (mandarin). Many varieties of bitter orange are used for their essential oil, and are found in perfume, used as flavouring or as a solvent. The Seville orange variety is used in the production of marmalade.