Ticks in the nostrils of humans visiting equatorial African forests have been reported sporadically for decades, but their taxonomy and natural history have remained obscure. We report human infestation with a nostril tick in Kibale National Park, Uganda, coincident with infestation of chimpanzees in the same location with nostril ticks, as shown by high-resolution digital photography. The human-derived nostril tick was identified morphologically and genetically as a nymph of the genus Amblyomma, but the mitochondrial 12S ribosomal RNA or the nuclear intergenic transcribed spacer 2 DNA sequences of the specimen were not represented in GenBank. These ticks may represent a previously uncharacterized species that is adapted to infesting chimpanzee nostrils as a defense against grooming. Ticks that feed upon apes and humans may facilitate cross-species transmission of pathogens, and the risk of exposure is likely elevated for persons who frequent ape habitats.