Nepeta cataria, commonly known as catnip, catswort, catwort, and catmint, is a species of the genus Nepeta in the Lamiaceae, native to southern and eastern Europe, the Middle East, Central Asia, and parts of China. It is widely naturalized in northern Europe, New Zealand, and North America. The common name catmint can also refer to the genus as a whole.

The names catnip and catmint are derived from the intense attraction about two-thirds of cats have toward it (alternative plants exist). In addition to its uses with cats, catnip is an ingredient in some herbal teas (or tisanes), and is valued for its sedative and relaxant properties.

Nepeta cataria is a short-lived perennial, herbaceous plant that grows to be 50–100 cm (20–40 in) tall and wide, and that blooms from late spring to autumn. In appearance, N. cataria resembles a typical member of the mint family of plants, featuring brown-green foliage with the characteristic square stem of the plant family Lamiaceae. The coarse-toothed leaves are triangular to elliptical in shape. The small, bilabiate catnip flowers of N. cataria are fragrant and are either pink in colour or white with fine spots of pale purple.

Nepeta cataria was one of the many species described by Linnaeus in 1753 in his landmark work Species Plantarum. He had previously described it in 1738 as Nepeta floribus interrupte spicatis pedunculatis (meaning "Nepeta with flowers in a stalked, interrupted spike"), before the commencement of Linnaean taxonomy.

With domestic cats, N. cataria is used as a recreational substance for the enjoyment of pet cats, and catnip and catnip-laced products designed for use with domesticated cats are available to consumers. Common behaviors cats display when they sense the bruised leaves or stems of catnip are rubbing on the plant, rolling on the ground, pawing at it, licking it, and chewing it. Consuming much of the plant is followed by drooling, sleepiness, anxiety, leaping about, and purring. Some growl, meow, scratch, or bite at the hand holding it. The main response period after exposure is generally between 5 and 15 minutes, after which olfactory fatigue usually sets in; however, about one-third of cats are not affected by catnip. The behavior is hereditary.