A chapbook is an item of popular literature, as would have formed part of the stock of a chapman, i.e. a pedlar , hawker or other itinerant trader. The term itself was coined by the bibliophiles of the nineteenth century; it can cover different kinds of printed matter, such as ballad sheets, pamphlets, tracts, and children's literature.

By their nature these tended to be cheaply produced ephemera, often flimsy and badly printed. Interest in them is as sources for popular culture, nursery rhymes and folk tales in early forms, popular politics and so on. Collectors such as Peter Opie created collections for purposes that were essentially scholarly. Political pamphlets were probably sought after first, by historians.

Chapbook is also a current term, for low-cost hard copy production particularly of poetry.