Acacia hamiltoniana, commonly known as Hamilton's wattle, is a species of flowering plant in the family Fabaceae and is endemic to New South Wales, Australia. It is an erect, bushy shrub with ascending to erect linear to lance-shaped or narrowly elliptic phyllodes, spherical heads of golden yellow flowers and firmly papery to thinly leathery, more or less black pods.
Acacia hamiltoniana is an erect or spreading, bushy shrub that typically grows to a height of with , finely ribbed, dark red branchlets. Its phyllodes are mostly ascending to erect, variably shaped, linear to lance-shaped with the narrower end towards the base, or narrowly elliptic, long, wide and glaucous to subglaucous with a vein on each side. The flowers are borne in spherical heads in racemes long on peduncles long, each head with nine to fifteen golden yellow flowers. Flowering occurs in August and September and the pods are up to long and about wide, firmly papery to thinly leathery, glabrous and more or less black. The seeds are oblong to elliptic or egg-shaped, long, somewhat shiny black with a club-shaped aril.
Acacia hamiltoniana was first formally described in 1920 by the botanist Joseph Maiden in the Journal and Proceedings of the Royal Society of New South Wales, from specimens collected by Arthur Andrew Hamilton near Leura. The specific epithet (hamiltoniana) honours Hamilton, who collected the type specimen in 1907.
Hamilton's wattle occurs on the Great Dividing Range and its foothills from near Rylstone and south to the Clyde River where it grows in sandy or loamy soils on sandstone outcrops in heath, Eucalyptus forest or woodland.