Oolong (simplified Chinese: 乌龙; traditional Chinese: 烏龍; pinyin: wūlóng) is a traditional Chinese tea (Camellia sinensis) produced through a unique process including withering under the strong sun and oxidation before curling and twisting. Most oolong teas, especially those of fine quality, involve unique tea plant cultivars that are exclusively used for particular varieties.The degree of fermentation can range from 8% to 85%, depending on the variety and production style. This tea category is especially popular with tea connoisseurs of south China and Chinese expatriates in Southeast Asia, as is the tea preparation process that originated from this area: gongfu tea-making, or the gongfu tea infusion approach.

In Chinese tea culture, semi-oxidised oolong teas are collectively grouped as qīngchá (Chinese: 青茶; literally "blue-green tea").The taste of oolong ranges hugely amongst various subvarieties. It can be sweet and fruity with honey aromas, or woody and thick with roasted aromas,or green and fresh with bouquet aromas, all depending on the horticulture and style of production.Several subvarieties of oolong, including those produced in the Wuyi Mountains of northern Fujian and in the central mountains of Taiwan, are among the most famous Chinese teas.

Different varieties of oolong are processed differently, but the leaves are formed into one of two distinct styles. Some are rolled into long curly leaves, while others are 'wrap-curled' into small beads, each with a tail. The former style is the more traditional of the two.

The name oolong tea came into the English language from the Chinese name (Chinese: 烏龍茶), meaning "black dragon tea".