Mamalia wa baharini ni mamalia wa majini ambao wanaishi na kupata riziki zao baharini. Ni wanyama wa spishi mbalimbali (129) jamii ya mamalia ambazo hazihusiani kwa asili, ila zimefuata njia zinazofanana kidogo katika kuzoea kwa kiasi tofauti mazingira hayo badala ya kuendelea kuishi katika nchi kavu. Kaschner, K.; Tittensor, D. P.; Ready, J.; Gerrodette, T.; Worm, B. (2011). "Current and Future Patterns of Global Marine Mammal Biodiversity". PLoS ONE 6 (5): e19653. doi:10.1371/journal.pone.0019653 . PMC 3100303 . PMID 21625431 . Pompa, S.; Ehrlich, P. R.; Ceballos, G. (2011-08-16). "Global distribution and conservation of marine mammals". Proceedings of the National Academy of Sciences 108 (33): 13600–13605. doi:10.1073/pnas.1101525108 . PMC 3158205 . PMID 21808012 . Perrin, W. F. (2009). [[[:Kigezo:Google books]] Encyclopedia of Marine Mammals], 2nd, San Diego: Academic Press. ISBN 978-0-0809-1993-5. OCLC 316226747.