San Lorenzo Creek is a 10.7-mile-long (17.2 km) year-round natural stream flowing through Hayward, California and other neighboring unincorporated communities into San Francisco Bay at the Hayward Regional Shoreline.

Hayward is a city located in Alameda County, California, United States, in the East Bay subregion of the San Francisco Bay Area. With a population of 162,954 as of 2020, Hayward is the sixth largest city in the Bay Area, and the third largest in Alameda County. Hayward was ranked as the 34th most populous municipality in California. It is included in the San Francisco–Oakland–San Jose Metropolitan Statistical Area by the US Census. It is located primarily between Castro Valley, San Leandro and Union City, and lies at the eastern terminus of the San Mateo–Hayward Bridge. The city was devastated early in its history by the 1868 Hayward earthquake. From the early 20th century until the beginning of the 1980s, Hayward's economy was dominated by its now defunct food canning and salt production industries.