San Diego Bay is a natural harbor and deepwater port adjacent to San Diego, California. It is 12 mi/19 km long, 1 mi/1.6 km–3 mi/4.8 km wide. The bay is surrounded by the large San Diego urban area and is bordered by the cities of San Diego, National City, Chula Vista, Imperial Beach and Coronado.
Considered to be one of the best natural harbors on the western coasts of the North American continent, San Diego Bay was among the earliest portions of those coasts to be settled by Europeans; it was colonized by Spain beginning in 1769. Later it served, and continues to serve to this day, as the home of the United States Navy’s Pacific Fleet.