Adenanthos is a genus of Australian native shrubs in the flowering plant family Proteaceae. Variable in habit and leaf shape, it is the only genus in the family where solitary flowers are the norm. It was discovered in 1791, and formally published by Jacques Labillardière in 1805. The type species is Adenanthos cuneatus, and 33 species are recognised. The genus is placed in subfamily Proteoideae, and is held to be most closely related to several South African genera.

Endemic to Australia, its centre of diversity is southwest Western Australia, where 31 species occur. The other two species occur in South Australia and western Victoria (Australia). They are mainly pollinated by birds.

The growth habits of Adenanthos species range from prostrate shrubs to small trees, with most species occurring as erect shrubs. There are two basic growth forms. Plants that lack a lignotuber have a single stem. Such plants usually grow into fairly erect shrubs; and sometimes the main stem thickens to become a trunk, resulting in a small tree. Plants with a lignotuber, on the other hand, have many stems arising from the underground rootstock, usually resulting in smaller shrubs with a mallee habit.

As with most other Proteaceae genera, leaf shape is highly variable in Adenanthos. Though the leaves are always simple (as in not compound), they may be lobed, or even deeply divided into segments, usually by three.

This segmentation has its extreme in the distinctive leaf form characteristic of those Adenanthos species known as woollybushes, in which the leaf is segmented, sometimes many times, into long thin laciniae, round in cross-section (terete), and often covered in a fine down of soft hairs. The number of laciniae varies greatly. In A. pungens, for example, the leaves may be entire, or there may be a single segmentation into two or three laciniae; in A. sericeus, the leaf is repeatedly tri-segmented into as many as 50 laciniae. This leaf form is seen in around half of the species.

Other common leaf forms include a wedge-shaped (cuneate) leaf with shallow lobes along the apex, seen, for example, in A. cuneatus and A. stictus; the oval-shaped (obovate) entire leaves of A. ellipticus and A. obovatus; and the long thin leaves of A. detmoldii and A. barbiger. Only two species have leaves that are sharply pointed (pungent): A. pungens has a woollybush form of leaf with pungent laciniae, and A. acanthophyllus is a flat (laminar), deeply lobed leaf with sharp points along its margins.

Some sources state that some leaves of some species are tipped with extrafloral nectaries.

Unusually for members of the family Proteaceae, Adenanthos flowers are solitary, rather than clustered together in large showy inflorescences. In fact, morphologically speaking, the Adenanthos flower does occur in an inflorescence, but one in which the number of flowers has been reduced to one, leaving only a few vestigial clues to the elaborate structure from which it derived. Each flower is positioned at the end of a short peduncle. The peduncle has minute basal bracts at its base, and sometimes at its midpoint, providing evidence of the loss of some lateral axes. At the end of the peduncle sits the flower, sessile or very nearly so, and surrounded at the base by an imbricate involucre. Very rarely, an involucre may enclose two flowers rather than just one, providing further evidence of reduction from a complex, multi-flowered inflorescence. Inflorescences occur individually at the end of branches (terminal) or at branch junctions (axillary). Most species have terminal inflorescences, and in these cases the inflorescences are usually subtended by leaves, if not branchlets, so the flowers are obscured by the foliage. The species with axillary inflorescences tend to be much more showy.