Interstate 805 (I-805) is a major north–south auxiliary Interstate Highway in Southern California. It is a bypass auxiliary route of I-5, running roughly through the center of the Greater San Diego region from San Ysidro near the Mexico–U.S. border to near Del Mar. The southern terminus of I-805 at I-5 in San Ysidro is less than 1 mi (1.6 km) north of the Mexican border. I-805 then traverses the cities of Chula Vista and National City before reentering San Diego. The freeway passes through the San Diego neighborhoods of North Park, Mission Valley, Clairemont, and University City before terminating at I-5 in the Sorrento Valley neighborhood near the Del Mar city limit.

Interstate 5 (I-5) is a major north–south route of the Interstate Highway System in the United States, stretching from the Mexican border at the San Ysidro crossing to the Canadian border near Blaine, Washington. The segment of I-5 in California runs 796.77 miles (1,282.28 km) across the length of the state from San Ysidro to the Oregon state line south of the Medford-Ashland metropolitan area. It is the longest interstate in California, and accounts for more than half of I-5's total length.