The Pacific sheath-tailed bat or Polynesian sheath-tailed bat (Emballonura semicaudata) is a species of sac-winged bat in the family Emballonuridae found in American Samoa, Fiji, Guam, Micronesia, Palau, Samoa (where it is called pe'a vai, tagiti or pe'ape'a vai), Tonga, and Vanuatu.