The San Gabriel Valley, often referred to by its initials as SGV, is one of the principal valleys of Southern California, with the city of Los Angeles directly bordering it to the west, and occupying the vast majority of the southeastern part of Los Angeles County. Surrounding landforms and other features include the following:the San Gabriel Mountains to the north; the San Rafael Hills to the west, with the Los Angeles Basin beyond; the Crescenta Valley to the northwest; the Puente Hills to the south, with the coastal plain of Orange County beyond; the Chino Hills and San Jose Hills to the east, with the Pomona Valley and Inland Empire beyond; and the city limits of Los Angeles, bordering its western edge.

Los Angeles, often referred to by its initials L.A., is the most populous city in the U.S. state of California. With roughly 3.9 million residents within the city limits as of 2020, Los Angeles is the second-most populous city in the United States, behind only New York City; it is also the commercial, financial and cultural center of Southern California. Los Angeles has an ethnically and culturally diverse population, and is the principal city of a metropolitan area of 13.2 million people. Greater Los Angeles, which includes the Los Angeles and Riverside–San Bernardino metropolitan areas, is a sprawling metropolis of over 18 million residents.