San Mateo Creek, Perennial stream in San Francisco Bay Area, California.

San Mateo Creek is a perennial stream about 7 miles (11.2 km) long that rises at nearly 1,000 feet on Sweeney Ridge and flows southeast into the northwest arm of Lower Crystal Springs Reservoir. Below Crystal Springs Dam it runs roughly 5 miles northeast through San Mateo, partly intermittent and altered, to San Francisco Bay about 0.7 miles west of Seal Slough's mouth. Its tributaries include San Andreas Creek and Laguna Creek.

The creek was first documented in 1769 when an expedition party encountered it while traveling through the area. Within a few years, other explorers also recorded the creek as they mapped and explored the region.

The Ssalson tribe of Ohlone people had three villages along San Mateo Creek and San Andreas Creek, named Altagmu, Aleitac, and Uturbe, as recorded by Mission San Francisco de Asís. By 1794, the tribe's members had moved to the mission. Juan Bautista de Anza's diary of March 29, 1776, describes the villagers as friendly and eager to serve.

San Mateo Creek rises on Sweeney Ridge at almost 1,000 feet and runs about 7 miles southeast into the northwest arm of Lower Crystal Springs Reservoir. Below Crystal Springs Dam it continues roughly 5 miles northeast through San Mateo, partly intermittent and altered, to San Francisco Bay about 0.7 miles west of Seal Slough's mouth. The causeway between the two reservoirs carries Highway 92.

San Mateo Creek once supported coho salmon and steelhead trout; Harvard professor Alexander Agassiz collected specimens there in the 1850s and 1860s. Historical records also place Chinook salmon in the watershed, one of only two San Francisco Bay Area streams with such records.