Mentzelia tricuspis is a species of flowering plant in the family Loasaceae known by the common name spinyhair blazingstar.

Mentzelia tricuspis is an annual herb growing erect or spreading to a maximum height near 27 centimeters.

The leaves are up to 12 centimeters long and toothed or wavy along the edges.

The inflorescence is a cluster of cream-colored flowers with petals up to 5 centimeters long and thready-tipped stamens.

The fruit is a cylindrical utricle up to 1.5 centimeters long which contains many tiny whitish beaked seeds.