Oolong, which means "black dragon" in Chinese, refers to tea leaves that have been oxidized about 20-30%, dried, and then lightly fired to bring out sweetness and body. The amount of caffeine in oolong tea is comparable to green tea, and research suggests that the health benefits are similar. (Other spellings include wu long, wulung, woolong.)

Oolong tea is most common in Taiwan (Formosa) and southeast China. Taiwan oolongs tend to be lighter and more flowery than the darker flavored oolongs of mainland China. Most oolong teas can be steeped several times.