We have observed among the holdings of Hymenostegia (Leguminosae: Caesalpinioideae) in several major herbaria that many of the specimens determined as H. klainei Pierre ex Pellegr. are not identified correctly and instead represent undescribed taxa. We speculate that the misidentifications may be a direct consequence of the sole use of leaf characters to distinguish species in the dichotomous keys of two major regional treatments of the genus. Two such previously unrecognised taxa, both new species from Gabon, Hymenostegia elegans Wieringa and Mackinder and Hymenostegia robusta Wieringa and Mackinder are described here accompanied by a distribution map, illustrations and conservation assessments. Both species have a limited distribution area and are assessed as Vulnerable and Endangered, respectively. This publication brings the total number of species in Hymenostegia s.s. to nine.