Arnica longifolia is a North American species of arnica in the sunflower family, known by the common names seep-spring arnica, longleaf arnica and spearleaf arnica. This flowering perennial is native to the forests of western Canada (British Columbia + Alberta) and the western United States (Rocky Mountains, Cascades, Coast Ranges, Sierra Nevada and other mountains of California, Oregon, Washington, Idaho, Nevada, Utah, Wyoming, Colorado, and Montana).