Plant-associated arthropods have been shown to cross large oceanic distances on floating plant material and to establish themselves on distant landmasses. Xyleborini (Coleoptera: Curculionidae: Scolytinae) ambrosia beetles occur in forests worldwide and are likely capable of long range dispersal. In less than 20 million years, this group dispersed from Asia to tropical regions of Africa and South America. The phylogeny, taxonomy, and biogeography of one Xyleborus species group which occurs on both continents are reviewed for this study. Based on a well-resolved molecular phylogeny resulting from parsimony, likelihood, and Bayesian analyses of four gene loci, we describe a new monophyletic genus, Xenoxylebora Osborn, Smith & Cognato, gen. nov., for this bicontinental Xyleborus species group with seven Afrotropical and six Neotropical species. Six new species are described: Xenoxylebora pilosa Osborn, Smith & Cognato, sp. nov. from Africa, and Xenoxylebora addenda Osborn, Smith & Cognato, sp. nov., Xenoxylebora calculosa Osborn, Smith & Cognato, sp. nov., Xenoxylebora hystricosa Osborn, Smith & Cognato, sp. nov., Xenoxylebora serrata Osborn, Smith & Cognato, sp. nov., and Xenoxylebora sulcata Osborn, Smith & Cognato, sp. nov., from South America. Seven new combinations from Xyleborus are proposed: Xenoxylebora caudata (Schedl 1957) comb. nov., Xenoxylebora collarti (Eggers 1932) comb. nov., Xenoxylebora perdiligens (Schedl 1937) comb. nov., Xenoxylebora sphenos (Sampson 1912) comb. nov., Xenoxylebora subcrenulata (Eggers 1932) comb. nov., and Xenoxylebora syzygii (Nunberg 1959) comb. nov. from Africa, and Xenoxylebora neosphenos (Schedl 1976) comb. nov. from South America. One new synonym is proposed: Xenoxylebora sphenos (Sampson 1912) = Xyleborus tenellus Schedl 1957 syn. nov. Descriptions, diagnoses, images, and a key to the identification of all 13 species are provided. The sequence of colonization between Africa and South America is uncertain for Xenoxylebora. Prevailing ocean currents and predominant locality patterns observed for other organisms suggest an African Xenoxylebora origin. However, the phylogeny, biogeographical analyses, and a calibrated divergence time suggest a possible South American origin for African Xenoxylebora (2.3 Ma, 95% HDP 4.5–0.6 Ma), which is supported by the occurrence of ocean counter currents between the continents and evidence of dispersal from South America to Africa among some plant and arthropod taxa.