Five new species of African Marantaceae are described and illustrated from two locations in Gabon, Marantochloa alba A. C. Ley, sp. nov., M. grandiflora A. C. Ley, sp. nov., M. montsdecristalii A. C. Ley, sp. nov. and Thaumatococcus flavus A. C. Ley, sp. nov. from the mountainous area of Monts de Cristal, north east of the capital Libreville, as well as Hypselodelphys lopei A. C. Ley, sp. nov. from the central part of Gabon in secondary forest near La Lope and Mikongo. New keys to the genera Marantochloa Brongn. & Gris., Thaumatococcus Benth. and Hypselodelphys (K. Schum.) Milne.-Redh. are provided.