Stenoma diametrica is a moth of the Depressariidae family. It is found in Colombia. The wingspan is about 18 mm. The forewings are violet-white, with a few scattered brown scales and a brown spot beneath the base of the costa and a light violet-grey band sprinkled brownish extending along the dorsum from the base to four-fifths, including a brown trapezoidal blotch resting on the dorsum before the middle, becoming blackish towards the dorsum, widened upwards and the discal edge twice dorsal. The first discal stigma forms a dark brown dash and the wing beyond a line from the middle of the costa to the tornus is chestnut-brown, enclosing a costal blotch of light ochreous suffusion, and some white suffusion at the apex, a white dot in the middle of the edge of this patch representing the seco