Jenner, also known as Jenner-by-the-Sea, is a small coastal town and census-designated place (CDP) in Sonoma County, California, United States, with a population of 122 per the 2020 Census. It is located on the Pacific coast near the mouth of the Russian River. State Route 1 runs through the town and State Route 116 runs nearby, along the Russian River. Immediately south of Jenner is Goat Rock Beach, a unit within the Sonoma Coast State Beach. Directly north, the Jenner Headlands Preserve offers scenic overlooks of the Jenner Estuary and surrounding areas.

Sonoma County is located in the U.S. state of California. As of the 2020 United States Census, its population was 488,863. Its seat of government and largest city is Santa Rosa.