We report bulk-sediment compositions of rare-earth elements and yttrium (REY), major and trace elements for “REY-rich mud” from 6 drill cores obtained by Ocean Drilling Program (Site 1215A, 1216A, 1217A, 1218A, 1220A and 1222A) off the southeastern coast of Hawaiian Islands. The REY-rich mud in study area has high REY contents, 400-1,178 ppm total REY (ΣREY), which are comparable to those of ion-absorption-type REY deposits in southern China. The core profiles indicate that the REY-rich mud has accumulated to thicknesses of 25-70 m. Some portions of REY-rich mud are typically enriched in Fe₂O₃, and their post-Archean average Australian shale (PAAS)-normalized REE patterns show strikingly negative Ce anomalies with the same magnitude of seawater. These geochemical characteristics are similar to those of modern hydrothermal Fe-rich sediments near the East Pacific Rise. This indicates that one of the main hosts for REY in the mud is a Fe-oxyhydroxide precipitate from hydrothermal plumes that has taken up REY from ambient seawater. On the other hand, the correlation diagram between ΣREY and Fe₂O₃ shows another ΣREY enrichment trend characterized by relatively low Fe contents, which infers an existence of the second REY-rich component. As the REY-rich samples on this trend contain significant amounts of phillipsite, the second REY-rich component is considered to be phillipsite. Here we estimate that a volume of 1 km² × Maximum Cumulated Concentration Depth (MCCD; in metric unit), which represents an appropriate mining depth, at Site 1222A holds nearly 12,200 t (14,000 tREO), which could provide one-tenth of the current annual world consumption of REY. We conclude that deep-sea REY-rich mud off the southeastern coast of Hawaiian Islands has a potential as a new mineral resource for REY.