Alsophila rosenstockii, synonym Cyathea ascendens, is a species of tree fern native to northeastern New Guinea, where it grows in rain forest at an altitude of . The erect trunk is slim and tall. Fronds are bi- or tripinnate and may be over in length. They form a distinctive open crown. The stipe is covered in glossy scales with pale, fragile edges. Sori occur near the midvein of fertile pinnules and lack indusia.