The Petaluma Gap is a geographical region in Sonoma County, California which extends in a band from the Pacific Ocean to San Pablo Bay. It is an area of low land 22 to 31 miles (35 to 50 kilometers) wide in the coast ranges of the northern San Francisco Bay Area. The western edge of the gap is located in the coastal lowlands between Bodega Bay and Tomales Bay. The eastern edge of the gap is located at San Pablo Bay around the mouth of the Petaluma River.