The 1984 Louisiana World Exposition was a world's fair held in New Orleans, Louisiana, United States. It was held 100 years after the city's earlier world's fair, the World Cotton Centennial in 1884. The fair was held from May 12 to November 11, 1984, and adopted the theme "The World of Rivers: Fresh Water as a Source of Life," showcasing the vital role of freshwater systems.

The 1984 Louisiana World Exposition encountered significant attendance challenges, ultimately becoming the only world's fair to declare bankruptcy during its operation. Several factors likely contributed to this. The exposition's proximity, both geographically and temporally, to the 1982 World's Fair in Knoxville, Tennessee, may have divided public interest. Additionally, the 1984 Summer Olympics in Los Angeles and the 1982 opening of Walt Disney World's Epcot (often referred to as a "permanent world's fair") presented substantial competition for visitors.

As of 2025, there has not been a world's fair in the United States since the 1984 Louisiana World Exposition.

The government of Louisiana spent $5 million on the fair; that amount was overseen by Ralph Perlman, the state budget director, who tried to obtain maximum use of the funds. An 84-acre (340,000 m²) site along the Mississippi River was cleared of rundown warehouses, replaced by the structures of the Fair. This was to be a "Class B" exposition as defined by the Bureau International des Expositions (BIE), the international body governing world's fairs. There were no major exhibits such as had been seen at the 1964–65 New York World's Fair, which started predictions that the fair could be a flop. Although 7 million guests toured the fair, it was not enough to recoup the $350 million spent to host the event. Paychecks started bouncing, and it was only through government intervention that the gates remained open through the scheduled run. The fair drew 30,000 fewer people in the first month than was predicted.

One of the fair's more famous attractions was the Mississippi Aerial River Transit (MART). This was a gondola lift that took visitors across the Mississippi River from the fair site in the Warehouse District to Algiers on the West Bank. Also on display was the Space Shuttle Enterprise.

The Fair was held along the Mississippi River front near the New Orleans Central Business District, on a site that was formerly a railroad yard. While the Fair itself was a financial failure, several old warehouses were renovated for the fair, which helped to revitalize the adjacent Old Warehouse District. The fair suffered from poor attendance, but many New Orleanians have fond memories of their fair experiences. Highlights included a monorail, a gondola across the Mississippi River, an aquacade, an amphitheater for concerts, the Wonderwall, and many dining choices, including the Italian Village, the Japanese Pavilion, and Pete Fountain's Reunion Hall.

U.S. Navy's host ship for the 1984 World's Fair was the USS Stump.

USS Lexington visited the fair and was open for tourist visits while much of the crew enjoyed liberty.