Allium, (genus Allium), large genus of onion- or garlic-scented bulbous herbs of the amaryllis family (Amaryllidaceae). Allium species are found in most regions of the world except the tropics and New Zealand and Australia. Several are important food crops, including the onion (Allium cepa), garlic (A. sativum), chive (A. schoenoprasum), and leek (A. porrum), and some are cultivated as ornamental border plants.

Allium species are characterized by pungent linear leaves and flowers with six petals. Many arise from bulbs or rhizomes, and most are perennials. The flowers are frequently borne in spherical flower clusters and produce black seeds in dry capsule fruits. Some plants reproduce asexually from bulbils in the flower head.