The San Lorenzo River is a 29.3-mile-long (47.2 km) river in the U.S. state of California. The name San Lorenzo derives from the Spanish language for "Saint Lawrence" due to its reported sighting on that saint's feast day by Spanish explorers. Its headwaters originate in Castle Rock State Park in the Santa Cruz Mountains and flow south by southeast through the San Lorenzo Valley before passing through Santa Cruz and emptying into Monterey Bay and the Pacific Ocean.

Santa Cruz is the largest city and the county seat of Santa Cruz County, in Northern California. As of the 2020 census, the city population was 62,956. Situated on the northern edge of Monterey Bay, Santa Cruz is a popular tourist destination, owing to its beaches, surf culture, and historic landmarks.