Willis Linn Jepson (August 19, 1867 – November 7, 1946) was an early California botanist, conservationist, and writer.

Born at Little Oak Ranch near Vacaville, California, Jepson became interested in botany as a boy and explored the adjacent San Francisco Bay Area.

In 1892, at the age of 25, Jepson, John Muir, and Warren Olney formed the Sierra Club, in Olney's San Francisco law office.

He was a professor of botany at UC Berkeley for four decades, thus his entire career was identified with the University of California.

Jepson founded the California Botanical Society and served as its president from 1913 to 1915; he also worked as councilor of the Rancho Santa Ana Botanic Garden.