Vexillum patulum, common name the wide-mouth mitre, is a species of small sea snail, marine gastropod mollusk in the family Costellariidae, the ribbed miters.
The length of the shell attains 18 mm.
(Original description) The ovate shell is rather thin, slightly ventricose, smooth. It is ash-coloured, variegated and clouded here and there with brown. The columella is four-plaited. The aperture is large. The outer lip is thin and sinuated at the upper part.
This marine species occurs off South Africa.