US Fish and Wildlife Service (FWS) and the National Marine Fisheries Service (NMFS; collectively, the "Services"), propose to revise portions of our regulations for section 4 of the Endangered Species Act of 1973, as amended (ESA or Act). The proposed revisions to the regulations clarify and interpret portions of the Act concerning the procedures and criteria used for listing, reclassifying, and delisting species on the Lists of Endangered and Threatened Wildlife and Plants and designating critical habitat. Comments must be received by 22 December 2025. POC is FWS/NMFS, U.S. Fish and Wildlife Service, Division of Conservation and Classification, fws@fws.gov, 703-358-2163; or FWS/NMFS, National Marine Fisheries Service, Office of Protected Resources, FWS/NMFS, 301-427-8466. (Federal Register 21 November 2025 [Proposed Rule] Pages 52607-52615).