Penn Valley is a census-designated place (CDP) in Nevada County, California. The population was 1,621 at the 2010 census, up from 1,387 at the 2000 census. The large Lake Wildwood master-planned community, although a separate CDP, has a Penn Valley postal address, and is sometimes considered part of the general Penn Valley community.

Nevada County is a county located in the U.S. state of California, in the Sierra Nevada. As of the 2020 census, its population was 102,241. The county seat is Nevada City. Nevada County comprises the Truckee-Grass Valley micropolitan statistical area, which is also included in the Sacramento-Roseville combined statistical area, part of the Mother Lode Country.