Stenoma ancillaris is a moth of the Depressariidae family. It is found in Brazil and the Guianas. The wingspan is about 16 mm. The forewings are light glossy violet-grey, with the costal edge whitish-ochreous and a black basal dot in the middle. The plical and second discal stigmata are black, the plical large. There is a slight blackish-grey oblique mark on the middle of the costa, and another at three-fourths, from which faint traces of a curved irregular series of dots proceed towards the tornus. A marginal series of small very indistinct blackish dots are found around the apex and termen. The hindwings are dark grey.