Allobenedenia Yamaguti, 1963 is revised to include capsalid species with five radial septa in the haptor. Megalocotyloides Bychowsky & Nagibina, 1967 and Allosprostonia Lawler & Hargis, 1968 are considered junior synonyms of Allobenedenia. Eight described species comprise the genus: A. convoluta (Yamaguti, 1937) Yamaguti, 1963 (type-species), A. epinepheli (Bychowsky & Nagibina, 1967) n. comb., A. patagonica (Evdokimova, 1969) n. comb., A. pedunculata Raju & Rao, 1980, A. pseudomarginata (Bravo-Hollis, 1958) n. comb., A. sebastodi (Egorova, 1994) n. comb., A. yamagutii (Egorova, 1994) n. comb. and A. zhangi n. sp. A. ishikawae (Goto, 1894) Yamaguti, 1963 is considered a species inquirenda; Megalocotyloides hongkongensis Wu, Lu & Woo, 2002 is placed in synonymy with A. yamagutii; M. grandiloba (Paperna & Kohn, 1964) Egorova & Aleshkina, 1984 is provisionally returned to Megalocotyle as M. grandiloba Paperna & Kohn, 1964; and specimens identified as M. grandiloba from Serranus cabrilla (Serranidae) by Buhrnheim et al. (1973) are considered an undescribed species of Allobenedenia. A. zhangi n. sp. is described from the external surface of Epinephelus fasciatus (Serranidae) of Allobenedenia. A. zhangi n. sp. is described from the external surface of Epinephelus fasciatus (Serranidae) in the South China Sea and is characterised by having an elongtate proximally uncoiled male copulatory organ extending to near the level of the anterior margin of the ovary, a large prostatic reservoir apparently external to the male copulatory canal, and a submedial protuberance on the dorsal surface of the accessory sclerite of the haptor.