Erigeron nauseosus is a North American species of flowering plant in the daisy family known by the common name Marysvale fleabane. It native to the western part of the United States, in northern Utah and Nevada. Erigeron nauseosus is a small perennial herb rarely more than 4 centimeters (1.6 inches) tall, producing a taproot. The leaves and the stem are covered with stiff hairs. The plant generally produces only 1 flower head per stem, each head with up to 35 blue or purple ray florets surrounding numerous yellow disc florets. The species grows on ridges, rocky slopes, and outcroppings.