It breeds in the Palearctic from Europe to the Caspian Sea and winters in South Africa, India, and Sri Lanka.

The terns are small to medium-sized seabirds, gull-like in appearance, but usually with a more delicate, lighter build and shorter, weaker legs.

[3] The Sandwich tern was originally described by ornithologist John Latham in 1787 as Sterna sandvicensis, but was moved to its current genus Thalasseus (Boie, 1822) following mitochondrial DNA studies which confirmed that the three types of head pattern (white crown, black cap, and black cap with a white blaze on the forehead) found among the terns corresponded to distinct clades.

[2] The current genus name is derived from Greek Thalassa, "sea", and sandvicensis, which, like the English name, refers to Sandwich, Kent, Latham's type locality.

The weight ranges from 200–300 g.[5] The Sandwich tern's thin, sharp bill is black with a yellow tip.

[7] The Sandwich tern is a vocal bird; its call is a characteristic loud grating kear-ik or kerr ink.

[1] The Sandwich tern is among the taxa to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

This plan should address key issues such as species and habitat conservation, management of human activities, research, education, and implementation.