Toward the northern end of its routing through Camp Pendleton, I-5 passes through San Onofre State Beach and near the San Onofre Nuclear Generating Station. It then follows the Pacific Ocean coastline for the next 18 mi (29 km). In Oceanside, I-5 intersects the SR 78 freeway and the SR 76 expressway and continues through Camp Pendleton. This segment is currently undergoing expansion as part of the North Coast Corridor project. North of the San Diego city limits, I-5 enters the city limits of Solana Beach, and then three incorporated cities to the north: Encinitas, Carlsbad and Oceanside. At this interchange, there is a local bypass that provides the only access to Carmel Mountain Road from both directions and provides the only direct access to SR 56 going northbound.

Shortly afterward, I‑5 passes through the UC San Diego campus and intersects the northern terminus of I-805 before continuing north and intersecting the western end of SR 56. At Nobel Drive, the San Diego LDS Temple towers over I-5. Thereafter, I-5 intersects the western end of SR 52 near La Jolla before entering University City. I-5 continues northwest from downtown as the San Diego Freeway until it reaches its junction with I-8, then turns slightly to the north while passing SeaWorld and Mission Bay.

I-5 southbound in San Diego toward Mexico, September 2012 Montgomery, a pioneer aviator who flew a glider from a location near Chula Vista in 1884. The portion of I-5 from the Mexican border to downtown San Diego is named the Montgomery Freeway in honor of John J. In addition to serving Downtown San Diego, I-5 also provides access to Balboa Park from the Pershing Drive exit. I-5 subsequently intersects with four state routes: the southern end of SR 15 (the extension of I-15), SR 75 and the Coronado Bay Bridge, the western end of SR 94, and SR 163. From there, I-5 veers around Naval Base San Diego and reenters the city limits of San Diego. It continues along the east side of San Diego Bay where it intersects with SR 54 and enters National City. I-5 then enters Chula Vista, briefly leaving the San Diego city limits. I-5 then continues northward and joins the southern end of SR 75, a highway connecting to Coronado via the Silver Strand. I-5 itself continues northwest and meets the western end of SR 905, a route that connects with the Otay Mesa border crossing. Immediately after the border, I-805 splits off to the northeast and serves as a bypass of I-5 that avoids Downtown San Diego. I-5 begins at the San Ysidro Port of Entry from Mexico in the San Ysidro neighborhood of San Diego. I-5 looking south toward Downtown San Diego, January 2002 I-5 is also eligible to be included in the State Scenic Highway System however, it is a scenic highway as designated by the California Department of Transportation (Caltrans) only from SR 152 to I-580. The segment of I-5 from State Route 89 (SR 89) to US 97 forms part of the Volcanic Legacy Scenic Byway, an All-American Road. I-5 is part of the California Freeway and Expressway System, and is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. 2.6 I-5W and the San Francisco Bay Area.I-5 has several named portions: the Montgomery Freeway, San Diego Freeway, Santa Ana Freeway, Golden State Freeway, and West Side Freeway. The San Francisco Bay Area is about 80 mi (130 km) west of the highway. This highway links the major California cities of San Diego, Santa Ana, Los Angeles, Stockton, Sacramento, and Redding. The highway connects to the Mexican Federal Highway 1 (Fed. 1) in the south. I-5 is known colloquially as 'the 5' to Southern California residents and '5' to Northern California residents due to varieties in California English. Route 101 (US 101), which is primarily coastal. It is the more important and most-used of the two major north–south routes on the Pacific Coast, the other being U.S. From San Ysidro, the segment of I-5 in California runs north across the length of the state, and crosses into Oregon south of the Medford- Ashland metropolitan area. 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. San Diego, Orange, Los Angeles, Kern, Kings, Fresno, Merced, Stanislaus, San Joaquin, Sacramento, Yolo, Colusa, Glenn, Tehama, Shasta, Siskiyou I-5 at Oregon state line south of Ashland, OR

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