The Southeast Asian cyprinid genus Crossocheilus was briefly described by Kuhl and van Hasselt in 1823 and, despite the short description, has remained a valid genus. However, the genus and its species are frequently misidentified in institutional collections, likely due to the absence of a detailed diagnosis and description, as well as the superficial morphological similarity with other cyprinid genera in the region. Crossocheilus and its constituent species are herein revised based on an examination of morphology and pigmentation. Eleven species are recognized, including a new species described from Indonesia. Crossocheilus pseudobagroidesis a junior synonym of C. langei. Crossocheilus tchangi is removed from synonymy with C. reticulatus and is a senior synonym of C. stigmaeus. Phylogenetic relationships among species of Crossocheilus based on sequences from the nuclear encoded recombination activating gene 1 are reconstructed. The resultant phylogeny is the most taxonomically comprehensive estimation of relationships among Crossocheilus to date and resolves C. atrilimes and C. oblongus, previously hypothesized to be sister species, not to be most closely related to one another.
