The moss genus Tortula is revised for South America. A key, descriptions, illustrations, distribution data, and light and scanning electron micrographs of the 11 species recognized are provided. A new species, Tortula arequipensis, is described from Peru. Twenty-six names are lectotypified. Thirty eight species are excluded from the genus Tortula. Six new combinations are proposed: Syntrichia breviseta, Syntrichia buchtienii, Syntrichia napoana, Syntrichia polylepidis, Syntrichia pseudolatifolia, and Tortula diaguita. Thirty-six names are newly synonymized. Previous records of Tortula vahliana from Chile correspond to Tortula platyphylla. Microbryum davallianum, Tortula cernua, Tortula hoppeana, and T. vahliana are newly reported for South America. In addition, new records for different countries of the study area are reported. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 173–220.