Plectris costulata is a species of beetle of the family Scarabaeidae. It is found in Brazil and Uruguay.
Adults reach a length of about 14 mm. The pronotum and scutellum are reddish-brown, the elytra dark brown and the legs and antennae light brown. The upper surface is glabrous, with at most a few short hairs at the margin in front of the elytra. The underside and pygidium are densely pubescent.