Clarkia biloba is a species of flowering plant in the evening primrose family known by the common name twolobe clarkia and two lobed clarkia.

Clarkia biloba is endemic to California, where it is known from the Sierra Nevada foothills; one subspecies can also be found in the San Francisco Bay Area. It grows in chaparral, oak woodlands, and yellow pine forest habitats.

As the putative progenitor species of Clarkia lingulata it is often used in examples of evolution outside the usual model of allopatric speciation. As such this plant is one of the best plant examples when considering "quantum speciation", a concept closely aligned with peripatric speciation, parapatric speciation and sympatric speciation.

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