Abomasal nematodes (Ostertagiine: Trichostrongyloidea) representing a previously unrecognized genus and species are reported in African buffalo (Syncerus caffer caffer) from Kenya, Uganda, and South Africa. Africanastrongylus buceros gen. nov. et sp. nov. is characterized by a symmetrical tapering synlophe in the cervical region and a maximum of 60 ridges in males and females. Bursal structure is 2–2–1, with subequal Rays 4/5, massive Rays 8, and Rays 9/10, and a massive dorsal lobe that is reduced in length, laterally and dorsally inflated, and positioned ventral to externodorsal rays. Spicules are tripartite, and the gubernaculum is broadly alate in the anterior. A proconus is present. Among ostertagiines with a 2–2–1 bursa (Cervicaprastrongylus, Hyostrongylus, Mazamastrongylus, Sarwaria, Spiculopteragia, and Teladorsagia) specimens of Africanastrongylus are differentiated from respective genera based on the structure of the cervical synlophe, patterns of dorsal, externodorsal, lateral, and ventral rays, and configuration of the genital cone, gubernaculum, and spicules. Among 13 genera of the Ostertagiinae in the global fauna, 3 are entirely limited in distribution to Africa, including Africanastrongylus, Longistrongylus, and Pseudomarshallagia. Another 5 genera including Cervicaprastrongylus, Hyostrongylus, Marshallagia, Ostertagia, and Teladorsagia are represented as mosaics, with diversity centered in Eurasia or the Holarctic. Genera not represented in the African fauna include Camelostrongylus among Caprinae and some Antelopinae from Eurasia, Mazamastrongylus and Spiculopteragia in Cervidae from the Holarctic and Eurasia, respectively, Orloffia in Cervidae and Bovidae from the Holarctic, and Sarwaria among Tragulidae and Bovinae in southern Asia. The diverse nature of the ostertagiine fauna, with a disproportionate number of endemic genera relative to other regions of the northern hemisphere, may reflect the timing of episodic expansion events for artiodactyls into Africa from Eurasia during the Tertiary and Quaternary.