Black tea is a tea made from leaves more heavily oxidized than the white, green, and oolong varieties. It is generally stronger in flavor and contains more caffeine than more lightly oxidized teas.  In Chinese and culturally related languages, black tea is known as red tea, perhaps a more accurate description of the color of the liquid.

While green tea usually loses its flavor within a year, black tea preserves its flavor for several years (over fifty years in the special case of Pu-erh tea). It has thus long been an article of trade, and compressed bricks of black tea even served as a form of 'de facto' currency in Mongolia, Tibet, and Siberia into the 19th Century. Black tea was traditionally the only tea known to Western culture; though green tea has been catching on somewhat in the U.S., black still accounts for over 90% of all tea sold in the West.

The term 'black tea' is also used in the United Kingdom to describe a cup of tea without milk; adding milk to tea being the accepted practice.