See text The Mimosoideae are a traditional subfamily of trees, herbs, lianas, and shrubs in the pea family (Fabaceae) that mostly grow in tropical and subtropical climates.

They are typically characterized by having radially symmetric flowers, with petals that are twice divided (valvate) in bud and with numerous showy, prominent stamens.

Recent work on phylogenetic relationships has found that the Mimosoideae form a clade nested with subfamily Caesalpinioideae and the most recent classification by The Legume Phylogeny Working Group refer to them as the Mimosoid clade within subfamily Caesalpinioideae.

In Bentham's 1842 circumscription of the subfamily Mimosoideae, Acacieae was one of its three constituent tribes, the others being Ingeae Benth.

[33] The only morphological character of Acacieae used to distinguish it from the Ingeae is the presence of free stamens (as in tribe Mimoseae).

[31][35] In the latter case, tribe Acacieae may conform to genus Acacia s.l., pending the latter's relationship to other mimosoid genera.

Faidherbia is troublesome as its stamens are shortly united at their base and its pollen is similar to some taxa in the Ingeae.

[38] Extrafloral nectaries may be present on the petiole and rachis, and the pinnule tips may carry protein-lipid Beltian bodies.

[38] The inflorescences are dense pedunculate heads or spikes borne in axillary clusters, or are aggregated in terminal panicles.

The flowers have numerous exserted (i.e. protruding) stamens (>2× as many as the corolla lobes),[34] and their filaments are sometimes connate at their base (forming a short stemonozone).