North County refers to the northern region of San Diego County which is the most affluent area of the county. Cities in North County include Oceanside, Escondido, Carlsbad, Vista, San Marcos, Encinitas, Poway, Solana Beach, and Del Mar. Some of the census-designated areas include Fallbrook, San Diego County Estates, Valley Center, Lake San Marcos, Bonsall, Hidden Meadows, Rancho Santa Fe, and Fairbanks Ranch. Other unincorporated areas include Pala Mesa, Pauma Valley, and Rincon. Camp Pendleton South and Pendleton Mainside are also located in North County. The city of San Diego is not located within North County.

Major lagoons and inlets along the North County coastline from north to south include Oceanside Harbor, Buena Vista Lagoon, Agua Hedionda Lagoon, Batiquitos Lagoon, and San Elijo Lagoon.

North County is home to California State University, San Marcos, a four-year university; MiraCosta College, a community college in Oceanside; and Palomar College, a community college in San Marcos.

The famous Paloma Observatory and Hale Telescope are located on Palomar Mountain in Palomar State Park which is in North County San Diego.

North County is famous for its numerous high quality golf courses. A partial list includes Torrey Pines South, Torrey Pines North, Aviara, La Costa, Maderas, Rancho Bernardo, The Crossings, Encinitas Ranch, The Vineyard, and Twin Oaks.

Other regions of San Diego County include South Bay, East County, and Central San Diego.