Acacia megacephala is a shrub of the genus Acacia and the subgenus Pulchellae that is endemic to south western Australia.
A. megacephala plants typically grow to a height of , with hairy branchlets that usually arch downwards and end with axillary spikes and linear-triangular shaped stipules that grow to a length of . The leaves are composed of one pair of pinnae with a length of which hold four to six pairs of green-grey, glabrous, oblanceolate pinnules with a length of and a width of . It blooms from July to September and produces yellow flowers.
The species was first formally described in 1972 by the botanist Bruce Maslin as a part of the work Studies in the genus Acacia as published in the journal Nuytsia. It was reclassified by Leslie Pedley in 2003 as Racosperma megacephalum then returned to genus Acacia in 2006.
It is native to an area in the Mid West regions of Western Australia, where it is commonly situated on sandplains growing in sandy or loamy soils. It has a limited range to around Geraldton as a part of in mixed scrub and shrubland communities.