Clarkia arcuata is a species of flowering plant in the evening primrose family known by the common name hairy clarkia. It is endemic to California, where it grows in the chaparral and woodlands of the foothills of the Sierra Nevada and southern Cascade Range. It is an annual herb producing a slender, erect stem often exceeding half a meter in height. The leaves are narrow, usually linear or lance-shaped, and up to 6 centimeters long. The flower cluster bears a few flowers, which dangle when they are buds and grow erect as they open. The sepals stay fused as the petals open and emerge from one side. They are coated in hairy hairs. The petals are up to 3 centimeters long, pink-lavender in color, sometimes with a reddish blotch at the base. They form a bowl-shaped corolla. There are 8 stamens and a protruding, four-chambered ovary. The fruit is an elongated capsule which may reach 3.5 centimeters long.