Ovula ovum, common name the common egg cowrie, is a species of sea snail, a marine gastropod mollusk in the family Ovulidae, the ovulids, cowry allies or false cowries.
The shells of these quite common cowries reach on average 65–70 millimetres (2.6–2.8 in) of length, with a minimum size of 50 millimetres (2.0 in) and a maximum size of 120 millimetres (4.7 in). They are egg-shaped (hence the Latin name ovum, meaning egg). The surface of the shell is smooth, shiny and completely snow white, with a dark reddish-purple interior, visible through the wide and long aperture, which bears teeth on one side only. In the living cowries the mantle is black, with a pattern of small white spots in adults, while juveniles resemble some toxic nudibranchs of the genus Phyllidia owing to their orange yellow sensorial papillae. The lateral flaps of the mantle usually hide completely the white surface, but the mantle is quickly retracted into the shell opening when the cowry is disturbed.