The Leek (Allium ampeloprasum var. porrum (L.) J. Gay) is a vegetable belonging, with onion and garlic.

Rather than forming a tight bulb such as the onion, the leek produces a long cylinder of bundled leaf sheaths which are generally blanched by pushing soil around them (trenching). They are often sold as small seedlings in flats which are started early in greenhouses, to be set out as weather permits. Once established in the garden, leeks are hardy; many varieties can be left in the ground during the winter to be harvested as needed.

Leeks are generally considered to have a finer flavor than the common onion. They are an essential ingredient of cock-a-leekie soup and of vichyssoise. They can also be used raw in salads, doing especially well when they are the prime ingredient.