Orocrambus angustipennis is a moth of the Crambinae family. It is known from New Zealand, where it is known from the North Island, South Island and the Chatham Islands. The wingspan is 34–40 mm for males and 44–50 mm for females. Adults are on wing from November to March in two generations per year. The larvae feed on Cortaderia, including Cortaderia selloana and Cortaderia toetoe. They feed within growing stems and blades.