Cabot's tern (Thalasseus acuflavidus) is a tern in the family Laridae formerly considered as a subspecies of the Sandwich tern. It has since been shown to be more closely related to the elegant tern (Thalasseus elegans). The genus name is from Ancient Greek Thalasseus, "fisherman" from thalassa, "sea". The specific acuflavida is Latin from acus, "needle", and flavidus, "yellowish". The IOC recognizes the bird as distinct, but most other taxonomists, including both committees of the AOU, consider it conspecific with the Sandwich tern.
The former species, T. s. eurygnatha (Saunders 1876), is sometimes treated as a separate species called the Cayenne tern (T. eurygnatha), which breeds on the Atlantic coast of South America from Argentina north to the Caribbean, intergrading with T. acuflavidus in the north of its range. The DNA analysis showed that Cayenne tern differed genetically from T. acuflavidus, but the difference was not sufficient to confirm it as a definite separate species