Leucopogon leptantha is a species of flowering plant in the heath family Ericaceae and is endemic to the south-west of Western Australia. It is an erect, bushy shrub that typically grows to a height of about . Its leaves are erect, oblong or egg-shaped and long with a small, hard point on the tip. The flowers are arranged singly or in pairs in leaf axils with small bracts and bracteoles less than half as long as the sepals. The sepals are about long, the petals joined at the base to form a tube about long with lobes about long.
The species was first formally described in 1868 by George Bentham in Flora Australiensis from specimens collected by James Drummond between the Moore and Murchison Rivers. The specific epithet (leptanthus) means "slender-flowered".
Leucopogon leptanthus occurs in the Geraldton Sandplains and Swan Coastal Plain bioregions of south-western Western Australia and is listed as "not threatened" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions.