Philo is a census-designated place in Mendocino County, California. It is located 5.5 miles (9 km) northwest of Boonville, at an elevation of 331 feet (101 m). The population was 349 at the 2010 census.
Philo is located in Anderson Valley in western Mendocino County. Situated along Indian Creek as it flows into the Navarro River, Philo is the home of KZYX, the local public radio station. Two small specialty lumber mills in Philo are all that remains of a once vigorous timber economy in Anderson Valley. Philo is the heart of the Anderson Valley wine region. (See Anderson Valley for a list of the region's winemakers.)
The first post office opened in 1888. The ZIP Code is 95466. The community is inside area code 707.
Two versions of how Philo was named are current: first, that its founder Cornelius Prather named it after his favorite female cousin; second, that he named it for his former home at Philo, Illinois.