The primarily Neotropical dolichoderine ant genus Linepithema is revised at the species level for the first time. Morphological and biogeographic data support the recognition of 19 species. The following taxonomic scheme is proposed: L. angulatum (Emery) stat. nov. [= pordescens (Wheeler) syn. nov.], L. dispertitum (Forel), L. flavescens (Wheeler & Mann) stat. nov., L. fuscum Mayr, L. gallardoi (Brèthes) [=breviscapa (Santschi) syn. nov. = impotens (Santschi) syn. nov.], L. humile (Mayr) [=arrogans (Chopard) = riograndense (Borgmeier)], L. iniquum (Mayr) [= bicolor (Forel) syn. nov. = dominicense (Wheeler) syn. nov. = fuscescens (Wheeler) syn. nov. = melleum (Wheeler) syn. nov. = nigellum (Emery) syn. nov. = succineum (Forel) syn. nov.], L. keiteli (Forel) [= subfaciatum (Wheeler & Mann) syn. nov.], L. leucomelas (Emery) [= aspidocoptum (Kempf) syn. nov.], L. micans (Forel) stat. nov. [= platense (Forel) syn. nov. = scotti (Santschi) syn. nov.], L. oblongum (Santschi), L. piliferum (Mayr). Seven species are described as new: L. anathema sp. nov., L. aztecoides sp. nov., L. cerradense sp. nov., L. cryptobioticum sp. nov., L. neotropicum sp. nov., L. pulex sp. nov., and L. tsachila sp. nov.. Seventeen species are sorted into one of four groups associated with the species L. fuscum, L. humile, L. iniquum, or L. neotropicum, and two species are left unassigned. New generic diagnoses are provided for worker, male, and queen castes, and Shattuck’s (1992a) generic descriptions of the worker, male, and queen castes are modified slightly to take into account expanded knowledge of character state variation. Worker and, where known, male and queen castes are described. Diagnoses, illustrations, and keys are supplied for worker and male castes. Discussions of variation, comparisons to similar species, and nomenclatural issues are given for each species, as well as synopses of life history traits such as queen number, colony structure, geographic distribution, nest site and habitat records, and associations with parasitoid Pseudacteon flies (Diptera: Phoridae).