Olbothrepta hydrosema is a moth in the Lecithoceridae family. It is found in southern India. The wingspan is 10-12 mm. The forewings are ochreous-yellow or ochreous, sometimes tinged with fuscous and with narrow irregular sometimes interrupted yellow-whitish or pale yellowish fasciae at one-third and beyond the middle, and an oblique discal mark between these. There is a rather inwardly oblique white transverse line from the costa at four-fifths, sometimes edged with dark fuscous irroration and a white apical elongate dot, one on the costa before it, and two on the termen. The hindwings are yellow-whitish, in males with the basal third of the costa clothed with long rough projecting ochreous-brown hairs.