We, NMFS, announce a final rule to list the chambered nautilus (Nautilus pompilius) as threatened under the Endangered Species Act (ESA). We have reviewed the status of the chambered nautilus, including efforts being made to protect this species, and considered public comments, including new information, submitted on the proposed rule. We have made our final determination based on the best scientific and commercial data available. At this time, we conclude that critical habitat is not determinable because data sufficient to perform the required analyses are lacking; however, we solicit information on habitat features and areas in U.S. waters that may meet the definition of critical habitat for the chambered nautilus.