Calochortus simulans is a species of flowering plant in the lily family known by the common name San Luis Obispo mariposa lily, not to be confused with the San Luis mariposa lily C. obispoensis. It is native to San Luis Obispo County, California, and its range extends south into Santa Barbara County. It is a perennial herb producing a branching stem up to 60 centimeters tall. The basal leaf is 10 to 20 centimeters long and withers by flowering. The flower cluster is a loose cluster of 1 to 3 erect, bell-shaped flowers. Each flower has three curving sepals and three longer petals, each up to 5 centimeters long. The petals are white to yellow with a deep red spot at the base. The fruit is an angled capsule 5 or 6 centimeters in length.