An orange—specifically, the sweet orange—is the citrus Citrus × sinensis (syn. Citrus aurantium L. var. dulcis L., or Citrus aurantium Risso) and its fruit.

The orange is a hybrid of ancient cultivated origin, possibly between pomelo (Citrus maxima) and mandarin (Citrus reticulata).

It is a small flowering tree growing to about 10 m tall with evergreen leaves, which are arranged alternately, of ovate shape with crenulate margins and 4–10 cm long.

The orange fruit is a hesperidium, a type of berry.