Alpine is a census-designated place (CDP) in the Cuyamaca Mountains of San Diego County, California. Alpine had a population of 14,696 at the 2020 census, up from 14,236 at the 2010 census. The town is largely surrounded by the Cleveland National Forest and borders two reservations of the Kumeyaay Nation, Viejas and Sycuan, and the rural unincorporated areas around the city of El Cajon.

The Cuyamaca Mountains, locally the Cuyamacas, are a mountain range of the Peninsular Ranges System, in San Diego County, southern California. The mountain range runs roughly northwest to southeast. The Laguna Mountains are directly adjacent to the east, with Palomar Mountain and Hot Springs Mountain more distant to the north.