Oranges are small to medium-sized, round fruits that are usually 5–10 centimeters in diameter. They are globular, oval, or oblate in shape, and their rind can be orange, yellow, or green. The rind is smooth and leathery, with small oil glands that produce essential oil.

Oranges are a modified berry called a hesperidium. The fruit is divided into segments, called carpels, which are made up of many small sections of juice.

The peel is waxy and protects the juice sacs. The peel has two layers: a thin outer layer called the flavedo, and a thicker, fibrous inner layer called the albedo. The flavedo contains carotenoids, which give oranges their color.

Oranges are low in calories and contain fiber, potassium, vitamin C, and folate. They may help prevent cancer and cardiovascular disease, and one cup of orange juice can provide 14% of a person's daily potassium requirement.