Promenesta triacmopa is a moth in the Depressariidae family. It was described by Meyrick in 1931. It is found in Paraguay. The wingspan is about 15 mm. The forewings are orange-yellow with the plical stigma minute and fuscous, the second discal forming a suffused round fuscous spot with a three-pointed whitish centre. There are faint minute brownish terminal dots. The hindwings are grey-whitish, with the termen slightly greyer-suffused.