Nine species of Hemirhamphiculus Bychowsky and Nagibina, 1969 (Dactylogyridae) were recorded from 6 beloniform fishes during a survey of the monogenoids infecting these fishes in the Gulf of Mexico off Florida from September 2017 through December 2020. Five new species were collected, illustrated, and described: Hemirhamphiculus acarips n. sp., Hemirhamphiculus longiclathra n. sp., and Hemirhamphiculus lucernula n. sp. all from Strongylura notata (Poey) and Hemirhamphiculus bilobatus n. sp. and Hemirhamphiculus litus n. sp. both from Strongylura timucu (Walbaum). Four previously described species were transferred to Hemirhamphiculus: Hemirhamphiculus tylosuri (MacCallum, 1917) n. comb. [formerly Ancyrocephalus tylosuri (MacCallum, 1917) Johnston and Tiegs, 1922]; Hemirhamphiculus parvus (Linton, 1940) n. comb. (formerly Ancyrocephalus parvus Linton, 1940); Hemirhamphiculus cornutus (Williams and Rogers, 1972) n. comb. (formerly Ancyrocephalus cornutus Williams and Rogers, 1972); and Hemirhamphiculus trullae (Williams, 1980) n. comb. (formerly Ancyrocephalus trullae Williams, 1980). The occurrence of He. trullae on Hyporhamphus meeki represents a new host record for the parasite. Three Indo-Pacific species of Dactylogyridae were transferred to Hemirhamphiculus: Pseudohaliotrematoides recurvatus Yamaguti, 1968, as Hemirhamphiculus recurvatus (Yamaguti, 1968) n. comb.; Tylosuricola haikouensis Zhang, 2001, as Hemirhamphiculus haikouensis (Zhang, 2001) n. comb.; and Xenentocleidus xenentodoni (Jain, 1961) Tripathi, Agrawal, and Pandey, 2007, as Hemirhamphiculus xenentodoni (Jain, 1959) n. comb. Xenentocleidus Tripathi, Agrawal, and Pandey, 2007, was synonymized with Hemirhamphiculus as its junior subjective synonym. Bychowskymonogenea Caballero and Bravo Hollis, 1972, and Bychowskymonogenea sogandaresi Caballero and Bravo Hollis, 1972, were placed as junior subjective synonyms of Hemirhamphiculus and He. tylosuri, respectively, and the Bychowskymonogeninae Caballero and Bravo Hollis, 1972, was rejected as a valid subfamily of the Dactylogyridae.