Nassarius speciosus, common name the purple-lipped dogwhelk or the splendid nassa, is a species of sea snail, a marine gastropod mollusc in the family Nassariidae, the nassa mud snails or dog whelks.

The aperture has a distinct siphonal notch, and the inner lip shows a well-developed callus that extends over both the columella and parietal region.

The outer lip has a subterminal external thickening and low internal ridges.

The surface of a living shell is often covered by a khaki-brown, periostracum-like layer formed by encrusting organisms.

[2] This marine species is endemic to South Africa and occurs off the West coast to Agulhas Bank (southern Namibia to western Transkei), in shallow water to 130 m, possibly deeper.