Linepithema (Mayr) is a Neotropical dolichoderine ant genus containing approximately 20 species of generalist foraging/scavenging ants. Male Linepithema ants are morphologically variable and highly divergent in comparison to the relatively generalized worker caste. Here I infer a phylogeny for Linepithema based on molecular data, including the mitochondrial gene COI and an intron of the nuclear gene wingless. Linepithema is found to be a well-supported lineage and sister to a clade of several old-world genera. At the species-level, molecular data largely confirm groupings suggested by male morphology, including a humile-group with compact males and a fuscum-group with elongate males. The mitochondrial tree is incongruent with morphology and with molecular data in several instances, and reasons for this incongruence are discussed. A sister species is suggested for the invasive Argentine ant L. humile.