Hymenoxys grandiflora is a North American species of flowering plant in the daisy family known by the common names graylocks four-nerve daisy, graylocks rubberweed, or old man of the mountain. It is native to high elevations in the Rocky Mountains of the western United States, in the states of Montana, Idaho, Wyoming, Utah, Colorado, and New Mexico. Hymenoxys grandiflora is a perennial herb up to 30 cm (1 foot) tall. One plant generally produces one flower head per stem, up to 10 per plant. Each head has 15–44 ray flowers and 150–400 disc flowers.