Recent studies have shown that the genus Acacia Mill. s.l. is polyphyletic, consisting of at least seven distinct groups of species. One of these groups, the proposed genus Parasenegalia Seigler & Ebinger, consists of seven species. We describe a new species, Parasenegalia lundellii Seigler & Ebinger, and make the following new combinations: Parasenegalia muricata (L.) Seigler & Ebinger, Parasenegalia rurrenabaqueana (Rusby) Seigler & Ebinger, Parasenegalia santosii (G. P. Lewis) Seigler & Ebinger, Parasenegalia skleroxyla (Tussac) Seigler & Ebinger, Parasenegalia visco (Lorentz ex Griseb.) Seigler & Ebinger, and Parasenegalia vogeliana (Steud.) Seigler & Ebinger. A second proposed genus, Pseudosenegalia Seigler & Ebinger, consists of two species: Pseudosenegalia feddeana (Harms) Seigler & Ebinger and Pseudosenegalia riograndensis (Atahuachi & L. Rico) Seigler & Ebinger. The species of Parasenegalia are widespread in the tropical areas of the Caribbean and scattered in Central and South America. Those of Pseudosenegalia are found in Bolivia. A series of morphological characteristics, as well as recent molecular data, separate these new genera from other members of Acacia subg. Aculeiferum Vassal. Although members of these two genera are distinct, previous taxonomic treatments have not dealt with them as separate units within Acacia subg. Aculeiferum. Lectotypes are designated for the following names: Acacia concinna Phil., Acacia polyphylla Clos, Acacia riparia Kunth var. angustifoliola Kuntze, Parasenegalia visco (Lorentz ex Griseb.) Seigler & Ebinger [≡ Acacia visco Lorentz ex Griseb.], and Pseudosenegalia feddeana (Harms) Seigler & Ebinger [≡ Acacia feddeana Harms].