Descriptions of two sister species, Begonia wollnyi Herzog and Begonia arrogans Irmsch., are provided and their distributions mapped and discussed. Begonia wollnyi is newly recorded from Peru and Argentina. Begonia parodiana L.B.Sm. & B.G.Schub. is newly synonymised with B. wollnyi. Begonia arrogans Irmsch. and two existing synonyms of B. wollnyi Herzog, Begonia acrensis Irmsch. and Begonia williamsii Rusby & Nash, are lectotypified. Begonia wollnyi and B. arrogans are both assessed as Least Concern (LC), according to IUCN criteria.