Lake Piru is an artificial lake located in Los Padres National Forest of Ventura County, California, created by the construction in 1955 of the Santa Felicia Dam on Piru Creek which is a tributary of the Santa Clara River. It is situated downstream from Pyramid Lake and can be accessed from Piru Canyon Road near the town of Piru, California. The elevation of the lake is 1,043 ft (318 m), and the elevation of the dam spillway is 1,055 ft (322 m).

The Lake Piru Recreation Area is an extensive campground around the lake with boating facilities, picnic areas, tent sites and other conveniences.

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land apart from a river, stream, or other form of moving water that serves to feed or drain the lake. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams, which are usually flowing. However most lakes are fed and drained by rivers and streams.

Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.

Many lakes are artificial and are constructed for industrial or agricultural use, for hydro-electric power generation or domestic water supply, or for aesthetic or recreational purposes.