Calochortus pulchellus is a rare species of flowering plant in the lily family known by the common name Mt. Diablo fairy-lantern. It is endemic to California, where it is mainly restricted to Mount Diablo in Contra Costa County. There are historical occurrences in surrounding counties. It grows in chaparral and woodland of the bayside slopes. This is a perennial herb growing a branching stem up to about 30 centimeters tall. The basal leaf is up to 40 centimeters long and does not wither at flowering; there are 2 or 3 smaller leaves farther up the stem. The flower cluster is a solitary flower or a cluster of several flowers, which are nodding and usually spherical with all their petal tips touching. The three sepals and three petals are 2 or 3 centimeters long and pale to deep yellow. The petals are thinly hairy inside and often fringed with yellow hairs. The fruit is a winged capsule 2 or 3 centimeters in length.