The Santa Ana Freeway is one of the principal freeways in Southern California, connecting Los Angeles and its southeastern suburbs including the freeway's namesake, the city of Santa Ana. The freeway begins at its junction with the San Diego Freeway, called the El Toro Y, in Irvine, signed as I-5. From there, it generally goes southeast to northwest to the East Los Angeles Interchange, where it takes the designation of U.S. Route 101 (US 101). It then proceeds 2.95 miles (4.75 km) northwest to the Four Level Interchange in downtown Los Angeles. Formerly, the entirety of the route was marked as US 101 until the 1964 highway renumbering, which truncated US 101 to the East Los Angeles Interchange and designated the rest of the freeway as I-5.

Santa Ana is a city in and the county seat of Orange County, California, United States. Located in the Greater Los Angeles region of Southern California, the city's population was 310,227 at the 2020 census, making Santa Ana the second most populous city in Orange County, the 13th-most populous city in California, and the 64th densest large city in the United States. Santa Ana is a major regional economic and cultural hub for the Orange Coast.