Symphyotrichum spathulatum (formerly Aster spathulatus) is a species of flowering plant in the family Asteraceae native to western North America including northwestern Mexico. Commonly known as western mountain aster, it is a perennial, herbaceous plant that may reach 20 to 80 centimeters (8 to 31 inches) tall. Its flowers, which open in July and August, have violet ray florets and yellow disk florets.