longan, (Dimocarpus longan), also spelled lungan, tropical fruit tree of the soapberry family (Sapindaceae), native to Asia and introduced into other warm regions of the world. The edible white-fleshed fruits are somewhat similar to the related lychee and are commonly sold fresh, dried, or canned in syrup.Longan (Dimocarpus Longan Lour.) is a subtropical fruit grown throughout Asia, with southern China including Taiwan being the main center of commercial production. The longan fruit is a famous summer fruit and is used as a TCM as a stomachic, febrifuge, and vermifuge, and also as an antidote to poison