Nannopterum is a genus of cormorant comprising three species. They are found throughout the Americas, hence the common name American cormorants.
Members of this genus were formerly classified within the genus Phalacrocorax, but a 2014 study found the members of this clade to represent a sister genus to Leucocarbo and reclassified them in the genus Nannopterum. The IOC followed this classification in 2021. It is thought to have split from Leucocarbo between 6.7 - 8.0 million years ago.
Nannopterum directly translates to "small-winged"; this name was originally coined as a monotypic genus name for the flightless cormorant (N. harrisi), which does indeed have small wings. Recent studies have also found the neotropic (N. brasilianum) and double-crested (N. auritum) cormorants to form a clade with the flightless cormorant, thus placing them in the genus Nannopterum despite both species having normal-sized wings and full flight capabilities. If the genus includes only the flightless cormorant, then the double-crested and neotropical cormorants would be assigned together to a separate genus, Nesocarbo.