The Large-billed Tern (Phaetusa simplex) is a species of tern in the Sternidae family.

It is found in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay, and Venezuela. It has occurred as a vagrant in Aruba, Bermuda, Cuba, Panama and the United States.

Its natural habitats are rivers and freshwater lakes.