Haesselia roraimensis gen. et spec. nov. (Cephaloziaceae) from the foot of Mt. Roraima (Guyana) is described and figured. The new genus has been assigned to the subfamily Trabacelluloideae together with Fuscocephaloziopsis Fulf. and Trabacellula Fulf., two other neotropical genera of Cephaloziaceae with convex leaves.