The 1939–1940 New York World's Fair was a world's fair held at Flushing Meadows–Corona Park in Queens, New York City, United States. It was the second-most expensive American world's fair of all time, exceeded only by St. Louis's Louisiana Purchase Exposition of 1904. Many countries around the world participated in it, and over 44 million people attended its exhibits in two seasons. It was the first exposition to be based on the future, with an opening slogan of "Dawn of a New Day", and it allowed all visitors to take a look at "the world of tomorrow".

A world's fair, also known as a universal exhibition or an expo, is a large global exhibition designed to showcase the achievements of nations. These exhibitions vary in character and are held in different parts of the world at a specific site for a period of time, typically between three and six months.