Porphyrosela alternata is a moth of the family Gracillariidae. It is known from Japan (the island of Kyà «shà «), Malaysia (the states of Pahang and Selangor), Nepal and Taiwan. This species is a well-known pest of cotton.
The wingspan is 2.6-4.3 mm.
The larvae feed on Desmodium species, including Desmodium heterocarpon, Desmodium heterophyllum and Desmodium strigillosum. They mine the leaves of their host plant.