This paper describes a new species of the genus Rhombognathus in the family Halacaridae (Acari: Prostigmata) under the name of Rhombognathus accrue sp. n. The material examined in the present study was collected at Labadi Beach on the coast of Accra in Ghana. Mites were recovered from small algae of the order Gigartinales in the phylum Rhodophyta on several rocks on the shore less than 0.5 m depth. Rhombognathus accrae is characterized by 1) dorsal plates ornamented with areolae, 2) anterior epimeral region with two adjunctive setae and posterior epimeral region with one adjunctive seta, 3) five perigenital and four subgenital setae in the female, 4) nine or 10 perigenital setae on each side of the genital foramen and four subgenital setae in the male, 5) telofemora I-IV with 4/3, 4/3, 3/0, 3/0 dorsal/ventral setae, genua I-IV with 5, 5, 3, 3 setae, 6) narrow palmate accessory process with about seven teeth. This is the first record of the genus from West Africa. A key to the African species of Rhombognathus is provided.