Aristogeitonia gabonica (Picrodendraceae) from the calcareous outcrops near Libreville, Gabon, is described and illustrated. This second species from western Africa is very different from the other, Angolan species, A. limoniifolia Prain by its large, unifoliolate leaves. It differs from the related east African A. monophylla Airy Shaw by its glabrous branchlets, the pilose anthers and by the female flower with pilose tepals and glabrous ovary. Its geography is discussed.