Banksia petiolaris is a species of shrub of the genus Banksia in the Proteaceae family. It is a prostrate banksia, a group of several closely related species all with horizontal stems and thick, leathery upright leaves. No varieties have been subsequently described. It bears yellow inflorescences in spring. It is found in sandy soils in the south coastal regions of Western Australia in the vicinity of Esperance. It is nonlignotuberous, regenerating by seed after bushfire. Banksia petiolaris adapts readily to cultivation, and is suitable for rockeries and as a groundcover.