The two subspecies are L. a. megalopterus — which can be seen from southeast Canada down to Central America — and L. a. atricilla, which appears from the West Indies to the Venezuelan islands.

The laughing gull was long placed in the genus Larus until its present placement in Leucophaeus.

The laughing gull was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae under the binomial name Larus atricilla.

[2] Linnaeus based his account on the "laughing gull" from the Bahamas that had been described and illustrated in 1729–1732 by the English naturalist Mark Catesby in his The Natural History of Carolina, Florida and the Bahama Islands.

The summer adult's body is white apart from the dark grey back and wings and black head.

Its wings are much darker grey than all other gulls of similar size except the smaller Franklin's gull, and they have black tips without the white crescent shown by Franklin's.

Northernmost populations migrate farther south in winter, and this species occurs as a rare vagrant to western Europe.