Clionella subventricosa is a species of sea snail, a marine gastropod mollusc in the family Clavatulidae.

The ovate, rather dark brown shell has a squat, fusiform shape.

The aperture is rather large with a rather narrow, slightly notched siphonal canal.

The color inside the aperture shows various shades of pale brown.

[3] This marine species occurs from False Bay to Cape Agulhas, South Africa