Orange juice is a primarily liquid extract of the orange tree fruit, produced by squeezing or reaming oranges. It comes in several different varieties, including blood orange, navel oranges, valencia orange, clementine, and tangerine. As well as variations in oranges used, some varieties include differing amounts of juice vesicles, known as "pulp" in American English, and "(juicy) bits" in British English. These vesicles contain the juice of the orange and can be left in or removed during the manufacturing process. How juicy these vesicles are depend upon many factors, such as species, variety, and season. In American English, the beverage name is often abbreviated as OJ.

Commercial orange juice with a long shelf life is made by pasteurizing the juice and removing the oxygen from it. This removes much of the taste, necessitating the later addition of a flavor pack, generally made from orange products. Additionally, some juice is further processed by drying and later rehydrating the juice, or by concentrating the juice and later adding water to the concentrate.

The health value of orange juice is debatable: it has a high concentration of vitamin C, but also a very high concentration of simple sugars, comparable to soft drinks. As a result, some government nutritional advice has been adjusted to encourage substitution of orange juice with raw fruit, which is digested more slowly, and limit daily consumption.

During World War II, American soldiers often rejected the vitamin C-packed lemon-flavored drink powder found in K-rations because of its unappetizing taste. Thus, the government searched for a better alternative that would fulfill the nutritional needs of the soldiers and prevent diseases such as scurvy while still having a desirable taste. The government and the Florida Department of Citrus worked with a group of scientists to develop a product superior to the canned orange juice available in the 1940s. The result was frozen, concentrated orange juice; this was not until three years after the war had ended.

By 1949, orange juice processing plants in Florida were producing over 10 million gallons of concentrated orange juice. Consumers liked concentrated canned orange juice as it was high in vitamin C, and they regarded it as affordable, tasty and convenient. The preparation was simple: empty the container of frozen concentrate into a measured volume of water and stir. However, by the 1980s, food scientists developed a fresher-tasting juice known as reconstituted ready-to-serve juice. Eventually in the 1990s, "not from concentrate" (NFC) orange juice was developed. Orange juice is a common breakfast beverage in the United States.

Due to the importance of oranges to the economy of Florida, "the juice obtained from mature oranges of the species Citrus sinensis and hybrids thereof" was adopted as the official beverage of Florida in 1967.

A cup serving (250 mL or 8 fluid ounces) of fresh orange juice is 88% water and contains 26 grams of carbohydrates (including 21 grams of sugar), two grams of protein, and 0.5 grams each of dietary fiber and fat (table). One cup supplies 112 calories and 149% of the Daily Value (DV) of vitamin C, with moderate amounts (11-19% DV) of potassium, thiamin, and folate (table).

Because of its citric acid content, orange juice is acidic, with a typical pH of around 3.5.