In the United States, a metropolitan statistical area (MSA) is a geographical region with a relatively high population density at its core and close economic ties throughout the area. Such regions are neither legally incorporated as a city or town would be, nor are they legal administrative divisions like counties or separate entities such as states; because of this, the precise definition of any given metropolitan area can vary with the source. The statistical criteria for a standard metropolitan area were defined in 1949 and redefined as metropolitan statistical area in 1983.

A typical metropolitan area is centered on a single large city that wields substantial influence over the region (e.g., New York City or Chicago). However, some metropolitan areas contain more than one large city with no single municipality holding a substantially dominant position (e.g., Dallas–Fort Worth metroplex, Virginia Beach–Norfolk–Newport News (Hampton Roads), Riverside–San Bernardino (Inland Empire) or Minneapolis–Saint Paul (Twin Cities)). MSAs are defined by the U.S. Office of Management and Budget (OMB) and used by the Census Bureau and other federal government agencies for statistical purposes.