Agonopterix l-nigrum is a moth in the Depressariidae family. It was described by Matsumura in 1931. It is found in Japan (Hokkaido) and the Russian Far East (Amur and Primorye regions). The wingspan is about 9 mm. The forewings are fuscous with a white basal patch bounded on the outside by a black line angled towards the costa. The costa is white, irrorated with chestnut in the centre of the cell at one-third to half. There is a black streak curved to the costal streak at the basal end.