The Sandwich tern ("Thalasseus sandvicensis") is a tern in the family Laridae. It is very closely related to the lesser crested tern ("T. bengalensis"), Chinese crested tern ("T. bernsteini"), Cabot's tern ("T. acuflavidus"), and elegant tern ("T. elegans") and has been known to interbreed with the lesser crested.
The Cabot's tern is very closely related to the elegant tern.