Juncus luciensis is a species of rush known by the common name Santa Lucia dwarf rush. It is endemic to California, where it is uncommon. This species is an annual herb growing just a few centimeters tall. It is yellowish green in color. The leaves are up to 1.5 centimeters long. The inflorescence contains one or two flowers with yellow-green tepals. The fruit is a greenish or sometimes red-tinged capsule containing seeds which are no more than 0.4 millimeters long.