Camissonia lacustris is a flowering plant species commonly called grassland suncup.

It is an evening primrose endemic to California, where it grows on the grasslands of the Sierra Nevada foothills.

It is an annual herb producing an erect or spreading, sometimes bending or twisting, hairy stem approaching half a meter in maximum length.

The leaves grow along the stem and are less than 4 centimeters long and linear or narrowly oval in shape.

The nodding inflorescence produces flowers with yellow petals about half a centimeter in length.