Monogenea van Beneden, 1858 is the most appropriate name to apply to the class of Platyhelminthes comprising the monogenean flatworms. Monogenoidea sensu Bychowsky (1937) is considered an emendation of Monogenea van Beneden, 1858. Arguments that support the use of Monogenoidea as the valid name of the class are based on erroneous assumptions of authorship and of “priority” and “rank”, as defined in the International Code of Zoological Nomenclature, a document that does not apply to taxa above the family level. In the absence of defined rules, names for higher taxa should be based on a combination of priority, stability and consensus among specialists, with stability and consensus the most important considerations. The priority of Monogenoidea versus Monogenea is questionable, and both nomenclatural stability and consensus among specialists favour the use of Monogenea rather than Monogenoidea.