Citrus is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, such as citrons, mandarins, and pomelos. Many important citrus crops have been developed through extensive hybridization, including oranges, lemons, grapefruits, and limes, all of which have many cultivars.

Citrus is native to South Asia, East Asia, Southeast Asia, Melanesia, and Australia. Indigenous people in these areas have used and domesticated various species since ancient times. Its cultivation first spread into Micronesia and Polynesia through the Austronesian expansion (c. 3000–1500 BCE). Later, it was spread to the Middle East and the Mediterranean (c. 1200 BCE) via the incense trade route, and then from Europe to the Americas.

Renowned for their highly fragrant aromas and complex flavor, citrus are among the most popular fruits in cultivation. With a propensity to hybridize between species, making their taxonomy complicated, there are numerous varieties encompassing a wide range of appearance and fruit flavors.

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