The gill monogeneans from the genus Ligophorus Euzet et Suriano, 1977 are parasites strictly host specific to mugilid fishes, occurring on a number of mullet species. In South Africa, monogeneans from marine and estuarine teleost fishes are still poorly known. During 2020, five individuals of the South African mullet Chelon richardsonii (Smith) were collected from the Groot River estuary on the south coast of South Africa (south-western Indian Ocean). Monogeneans collected from the gills were preserved for morphological and phylogenetic analyses. The monogeneans found were morphologically identified as Ligophorus minimus Euzet et Suriano, 1977. This study provides the first record of L. minimus from South Africa and the first record on the host C. richardsonii. Furthermore, sequences of the partial 28S rRNA gene and the entire ITS1 region for this species were obtained from the sampled locality in the south-western Indian Ocean for the first time. Phylogenetic analyses confirmed the morphological identification of L. minimus in the present study. The phylogenetic relationships of L. minimus with its congeners corroborate previous studies, providing more insights into the monophyly of the genus, routes of new host colonisation, and distribution patterns.