Erigeron decumbens is a species of flowering plant in the aster family known by the common name Willamette fleabane. It is native to Oregon and California in the United States. The taxonomy of the plant varies by author. It may be treated as a species with two varieties, the Californian variety var. robustior and the rare and endangered Oregon variety, var. decumbens. Alternately, the rare var. decumbens may be the only variety included within the species description and so named Erigeron decumbens, with var. robusta separated and named Erigeron robusta.