Nestotus stenophyllus is a species of flowering plant in the aster family known by the common name narrowleaf mock goldenweed. It is native to the western United States, especially the inland Pacific Northwest and northern Great Basin, where it grows in sagebrush habitat. It is a small, clump-forming perennial herb growing up to about 12 centimeters tall. The rough-haired, glandular leaves are 1 or 2 centimeters long and linear to lance-shaped. The inflorescence is a solitary flower head atop an erect peduncle. The hairy head has several yellow disc florets each around a centimeter long and at the center many yellow disc florets. The fruit is a silky-haired achene tipped with a white pappus.