San Francisco is a city in Western California, in the United States of America.

Famous for its beautiful setting, San Francisco is built on a series of steep hills located on the Northern tip of a peninsula at the entrance to San Francisco Bay. The bay and its extensions, which include San Pablo Bay and Suisun Bay, constitute one of the great natural harbors of the world, embracing nearly 1,200 sq km (more than 450 sq mi) of water.

Because of this, San Francisco was once the major Pacific Coast seaport of the United States. Today the city is an important center for finance, technology, tourism, and culture.

Coextensive with San Francisco County, the city was named after San Francisco Bay, which in turn was named for Saint Francis of Assisi by early Spanish explorers.

The cool waters of the ocean and bay surround San Francisco on three sides, moderating the climate, which is characterized by mild, rainy winters and cool, dry summers.