Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. The genus Citrus is native to South Asia, East Asia, Southeast Asia, Melanesia, and Australia. Various citrus species have been used and domesticated by indigenous cultures in these areas since ancient times. From there its cultivation spread into Micronesia and Polynesia by the Austronesian expansion ; and to the Middle East and the Mediterranean via the incense trade route, and onwards to Europe and the Americas.

निम्बू-वंश एक पादप वंश है, जो रुटेसी (Rutaceae) कुल के पुष्पीय पादपों का वंश है। इनकी उत्पत्ति दुनिया के उष्णकटिबंधीय और उपोष्ण दक्षिण पूर्वी क्षेत्रों में हुई है।