Kumquats ( KUM-kwot), sometimes spelled cumquat in Australian English and British English, are a group of small, angiosperm, fruit-bearing trees in the family Rutaceae. The edible fruit closely resembles the orange (Citrus x sinensis) in color, texture, and anatomy, but is much smaller, being approximately the size of a large olive. They are native to southern China but have been cultivated for centuries in Japan and Southeast Asia. The kumquat is a fairly cold-hardy citrus.
The taxonomy of kumquats is disputed. They were once classified as forming the historical genus Fortunella or placed within Citrus, sensu lato. Different classifications have assigned them ranging from a single species, Citrus japonica, to numerous species representing each cultivar. Recent genomic analysis defines three pure species, Citrus hindsii, C. margarita and C. crassifolia, with C. × japonica being a hybrid of the last two.