Altadena (AL-tə-DEE-nə) is an unincorporated area, and census-designated place in the San Gabriel Valley and the Verdugos regions of Los Angeles County, California. Directly north of Pasadena, it is located approximately 14 miles (23 km) from Downtown Los Angeles. Its population was 42,846 at the 2020 census, up slightly from a 2010 figure of 42,777. In early 2025, the community was severely impacted by the Eaton Fire.