For the publishing use of the term 'leaflet', see pamphlet.

A leaflet in botany is a part of a compound leaf. A leaflet may resemble a complete leaf, but it is not borne on a stem as a leaf is, but rather on a vein of the whole leaf. Compound leaves are common in many plant families.

Leaflets borne on the central vein of a leaf are referred to as pinnae; the compound leaves themselves are described as pinnate. A plant may be further subdivided in that the pinnae are themselves split into leaflets, or pinnules; these leaves are now twice pinnate, or bipinnate. A few plant species even have tripinnate leaves.