Susan Lynn Williams (June 21, 1951 – April 24, 2018) was an American marine biologist and Distinguished Professor of Evolution and Ecology at the University of California, Davis, where she directed the Bodega Marine Laboratory from 2000-2010. She researched marine coastal ecosystems (in particular seagrass, seaweed, and coral reef habitats) and how they are affected by human activities. She was a strong advocate for environmental protection, credited with helping pass legislation expanding the boundaries of Northern California's Gulf of the Farallones and Cordell Bank national sanctuaries, increasing the area of federally-protected coastal waters.