Olsynium douglasii (syn. Sisyrinchium douglasii, Sisyrinchium grandiflorum) is a flowering plant in the genus Olsynium, native to western North America from southern British Columbia south to northern California, and east to northwest Utah. It is the only species in the genus Olsynium in North America, the remaining 11 species being from South America. It was formerly treated in the related genus Sisyrinchium. It is a perennial herbaceous bulbiferous plant growing to 10-40 centimeter tall. The leaves are slender linear, 10-30 centimeter long and 1.5-3 millimeter broad. The flowers are bell-shaped, 15-25 millimeter long, with six purple petals.