The US Southeast is the eastern portion of the Southern United States, but the Census Bureau does not provide a standard definition of a "Southeast" region of the United States, and organizations that need to subdivide the US are free to define a "Southeast" region to fit their needs.  However, Georgia is almost always included, Texas is rarely included, and inclusion of other states varies.
Metropolitan Atlanta is the main population center of the Southeast  , and the Southeast roughly corresponds to an area with Atlanta centrally located, with Hartsfield-Jackson as the region's airline hub. Atlanta has the third-largest concentration of colleges and universities and also college students, with over 30 institutions and over 280,000 students. Much of Virginia is associated with the Washington, Richmond or Virginia Beach-Norfolk-Newport News metropolitan areas. A portion of the latter extends into North Carolina.
Research Triangle Park, in the Raleigh-Durham urban area of North Carolina has emerged (over a nearly 50-year existence) as a major hub of technology, governmental and biotechnological research and development, as has the Virginia BioTechnology Research Park in Richmond. The Cummings Research Park in the Huntsville, Alabama area is the second largest research complex in the nation. It is one of the biggest areas of aerospace engineering and missile defense technology. The National High Magnetic Field Laboratory in Tallahassee, Florida is the largest laboratory in the world devoted to the study of magnetism. The University of South Carolina is currently constructing a research campus in downtown Columbia, and the University is the nation’s only National Science Foundation-funded Industry/University Cooperative Research Center for Fuel Cells.
Beyond Megalopolis by Virginia Tech's Metropolitan Institute, an attempt to update Jean Gottmann's work with current trends, defines two "megapolitan areas" contained within the Southeast, out of a total of ten such areas in the United States:
Two others tie some areas on the margins of the Southeast to urban centers in other regions:
|Rank||Metropolitan Area||Anchor City||Population||State(s)|
|1||Atlanta-Sandy Springs-Gainesville||Atlanta||5,729,304||Georgia / Alabama|
|2||Miami-Fort Lauderdale-Pompano Beach||Miami||5,414,772||Florida|
|3||Washington-Arlington-Alexandria||Washington D.C.||5,358,130||Virginia / District of Columbia / Maryland / West Virginia|
|5||Charlotte-Gastonia-Salisbury||Charlotte||2,338,289||North Carolina / South Carolina|
|8||Virginia Beach-Norfolk-Newport News||Norfolk||1,658,292||Virginia / North Carolina|
|10||Greensboro--Winston-Salem--High Point||Greensboro||1,552,495||North Carolina|
|13||Memphis||Memphis||1,285,732||Tennessee / Mississippi / Arkansas|