The South American genus of mailed catfishes Loricaria Linnaeus, 1758 is reviewed. Almost all primary type-material and additional specimens are examined. Descriptions, tabulated morphometric and meristic data, and illustrations are presented of eleven species: Loricaria cataphracta Linnaeus, 1758 (syn.: Plecostomus flagellaris Gronovius, ed. Gray, 1854, and Loricaria carinata de Castelnau, 1855), L. lata Eigenmann & Eigenmann, 1889, L. simillima Regan, 1904, L. parnahybae Steindachner, 1907 (syn.: L. piauhiae Fowler 1941), L. piracicabae Von Ihering, 1907, L. clavipinna Fowler, 1940, L. nickeriensis Isbrücker, 1979, L. tucumanensis Isbrücker, 1979, L. apeltogaster Boulenger, 1895, L. prolixa Isbrücker & Nijssen, 1978, and L. lentiginosa Isbrücker, 1979. The nomenclatural history of L. cataphracta is revised: contrary to the author’s previous (1972) assumption, two syntypes of this species are still in existence. Definitions are presented of the tribe Loricariini, the subtribe Loricariina, the Loricariaand Pseudohemiodon-groups, and of the Loricaria cataphracta species complex. In addition, the Pseudoloricariina (new subtribe), the Ricolina (new subtribe), and the Planiloricariina are defined. A key to the genera of Loricariinae with filamentous lip structures is given. A list of species originally proposed as representatives of the genus Loricaria, now excluded, is added together with their current identification.