The Guadalupe murrelet (Synthliboramphus hypoleucus) or Xantus' Murrelet is a small seabird found in the California Current system in the Pacific Ocean. This auk breeds on islands off California and Mexico. It is threatened by predators introduced to its breeding colonies and by oil spills.
This species together with the Scripps's murrelet were considered conspecific and were classified under S. hypoleucus; known collectively as Xantus's murrelet until 2012. Enough evidence was collected to consider both species distinct based on a lack of evidence of interbreeding where the two species nest together on the San Benito Islands, differences in facial pattern and bill shape, vocalizations and genetics.