Coronado is a resort city located in San Diego County, California, United States, across the San Diego Bay from downtown San Diego. It was founded in the 1880s and incorporated in 1890. Its population was 20,192 in 2020, down from 24,697 in 2010.

San Diego Bay is a natural harbor and deepwater port located in San Diego County, California near the U.S.–Mexico border. The bay, which is 12 miles (19 km) long and 1 to 3 miles wide, is the third largest of the three large, protected natural bays on California's 840 miles (1,350 km) of coastline, after San Francisco Bay and Humboldt Bay. The highly urbanized land adjacent to the bay includes the city of San Diego and four other cities: National City, Chula Vista, Imperial Beach and Coronado.