Piru ( /paɪruː/ "Pie-roo") is a small unincorporated census-designated town located in eastern Ventura County, California, in the Santa Clara River Valley near the Santa Clara River and Highway 126, about seven miles (11 km) east of Fillmore and about 13 miles (21 km) west of Interstate 5. The population was 2,063 at the 2010 census, up from 1,196 when the 2000 census was enumerated. Lake Piru, in the Los Padres National Forest, is the main recreational attraction.
The area was originally inhabited by the Tataviam Indians. They left information about themselves chiseled into and painted on rocky overhangs and secreted caves throughout the local mountains. By all accounts a peaceful tribe, the Tataviam were christianized under the San Fernando Mission. Later they worked on large Spanish ranchos such as Rancho Camulos.
The name Piru (originally pronounced "Pea-roo" by the Indians) comes from the Tataviam word for the tule reeds growing along Piru Creek that were used in making baskets.