Otocinclus is a genus of catfish in the family Loricariidae native to South America, commonly known as "dwarf suckers" or "otos".

A duct forms at the junction between the esophagus and the stomach and expands into an enlarged, ring-like diverticulum, characteristic of this genus, which allows air-breathing.

[8] Species of this genus are diurnal and generally are found in small streams or along the margins of larger rivers, clinging to substrates using their suckermouth.

The fish of this genus primarily feed on algae or aufwuchs on roots, stones, macrophytes and broad-leaved grasses.

Upon returning to the bottom, the fish do not need to pump their buccal cavities, indicating they are absorbing oxygen from the swallowed air.

[2] O. flexilis, O. mimulus and O. xakriaba are considered to be Batesian mimics of certain Corydoras species (C. diphyes, C. garbei, C. nattereri and C. paleatus, respectively).