The genus Thymus (/ˈtaɪməs/ TY-məs; thymes) contains about 350 species of aromatic perennial herbaceous plants and subshrubs in the family Lamiaceae. It is native to the Old World.

Several members of the genus are cultivated as culinary herbs or ornamentals, when they are also called thyme after its best-known species, Thymus vulgaris or common thyme.

The plants grow up to 40 centimetres (16 in) tall. The stems tend to be narrow or even wiry. The leaves are evergreen in most species, arranged in opposite pairs, oval, entire, and small, 4–20 millimetres (1⁄8–3⁄4 in) long, and usually aromatic. Thyme flowers are in dense terminal heads with an uneven calyx, with the upper lip three-lobed, and are yellow, white, or purple.

A considerable amount of confusion has existed in the naming of thymes. Many nurseries use common names rather than binomial names, which can lead to mix-ups. For example golden thyme, lemon thyme, and creeping thyme are all common names for more than one cultivar. Some confusion remains over the naming and taxonomy of some species, and Margaret Easter (who holds the NCCPG National Plant Collection of thymes in the UK) has compiled a list of synonyms for cultivated species and cultivars.

The most common classification is that used by Jalas, in eight sections:

The genus is native to temperate regions in Europe, North Africa and Asia. Thymus is particularly concentrated in Iran, attributed to the country's diverse climate and location both in terms of geography and topography. Thymus quinquecostatus Celak is present in Korea.

Thymus species are used as food plants by the larvae of some butterfly and moth insect species, including Chionodes distinctella and the Coleophora case-bearers C. lixella, C. niveicostella, C. serpylletorum, and C. struella (the last three feeding exclusively on Thymus).

Thymus is cultivated for its fragrant leaves and used as a culinary herb in Mediterranean cooking.