Ocean sunfishes, family Molidae, are some of the most heavily parasitized fish in the world, but there is scarce knowledge regarding the effects of such associations. More broadly, understanding their parasite fauna provides insights into their somewhat cryptic dietary choices, and even population connectivity. In this chapter, the parasitic fauna of this remarkable family is reviewed, including a checklist with parasite location and localities. Seventy-three parasitic species are reported (from 54 genera)-the bulk of species being either helminths or arthropods. Sixty-six parasitic species are reported from Mola mola, 17 from M. alexandrini, five from Masturus lanceolatus, and three from Ranzania laevis. The existence and benefits of parasitic cleaning events are also discussed. The baseline research reviewed herein provides essential groundwork for identifying and addressing existing knowledge gaps and pursuing fruitful future research.