The Hatchetigbee Bluff Formation is a geologic unit in the southern United States, occurring in Alabama, Georgia, Louisiana, and Mississippi. Named for Hatchetigbee Bluff on the Tombigbee River in Washington County, Alabama, it is the youngest unit of the Wilcox Group. The formation preserves fossils from the Ypresian stage of the Eocene, corresponding to the Wasatchian in North American land mammal ages. Those fossils have made it important to the study of early Paleogene environments and life in the Gulf Coastal Plain, including research on marine ecosystems and Eocene molluscs.