The Rust Belt is a region of the United States that experienced industrial decline starting in the 1950s. The U.S. manufacturing sector as a percentage of the U.S. GDP peaked in 1953 and has been in decline since, impacting certain regions and cities primarily in the Northeast and Midwest regions of the U.S., including Allentown, Buffalo, Cincinnati, Cleveland, Columbus, Detroit, Jersey City, Newark, Pittsburgh, Rochester, Toledo, Trenton, Youngstown, and other areas of New Jersey, Ohio, Pennsylvania, and Upstate New York. These regions experienced and, in some cases, are continuing to experience the elimination or outsourcing of manufacturing jobs beginning in the late 20th century. The term "Rust" refers to the impact of deindustrialization, economic decline, population loss, and urban decay on these regions attributable to the shrinking of the once-powerful industrial sector especially including steelmaking, automobile manufacturing, and coal mining. The term gained popularity in the U.S. beginning in the 1980s when it was commonly contrasted with the Sun Belt, which was surging.

The Rust Belt runs southwesterly from Central New York through Pennsylvania, Ohio, West Virginia, Kentucky, Indiana, and then northwesterly through the Lower Peninsula of Michigan, northern Illinois, and ends in northeastern Wisconsin. New England was also hard hit by industrial decline during the same era. Since the mid-20th century, heavy industry has declined in the region, formerly known as the industrial heartland of America.

Causes include lack of competition in the labor markets due to unionization and lack of competition among firms leading to stagnation. Cities closer to the East Coast like the New York Metropolitan Area, and the Boston area have been able to adapt by diversifying or transforming their economies to shift focus towards services, advanced manufacturing, and high-tech industries. Others have not fared as well, experiencing economic distress with poverty and the resulting decline in population.