Dawn Yvonne Sumner is an American geologist, planetary scientist, and astrobiologist. She is a professor at the University of California, Davis. Sumner's research includes evaluating microbial communities in Antarctic lakes, exploration of Mars via the Curiosity rover, and characterization of microbial communities in the lab and from ancient geologic samples. She is an investigator on the NASA Mars Science Laboratory (MSL) and was Chair of the UC Davis Department of Earth & Planetary Sciences from 2014-2016. She is Fellow of the Geological Society of America.