Miralda diadema is a species of sea snail, a marine gastropod mollusc in the family Pyramidellidae, the pyrams and their allies.

It is subovate, minutely umbilicated, with the summits of the whorls decidedly tabulated.

They are ornamented by rounded, axial ribs which quickly diminish in strength as they pass from the summit of the whorls to the periphery.

The ribs are thickened at the anterior termination of the shoulder and render it decidedly crenulated.

The junction of the posterior one of these two cords and the axial ribs form a series of tubercles.