Agonopterix petraea is a moth in the Depressariidae family. It was described by Meyrick in 1910. It is found in Sri Lanka. The wingspan is 17–22 mm. The forewings are dark purple-fuscous, with scattered rough black scales and more or less pale ochreous irroration towards the costa anteriorly. The first discal stigma represented by two very obliquely placed small tufts of black and whitish-ochreous scales and the second by a larger mostly black transverse tuft. There is a curved patch of undefined brownish suffusion in the disc posteriorly and an undefined black terminal line interrupted with whitish-ochreous. The hindwings are thinly scaled, bronzy-fuscous, with darker veins.