The city is named after George Washington, military leader of the American Revolution and the first President of the United States.

The District of Columbia and the city of Washington are coextensive and are governed by a single municipal government. For most practical purposes, they are considered to be the same entity, though this was not always the case. As late as 1871, when Georgetown ceased to be a separate city, there were multiple jurisdictions within the District. Although there is a municipal government and a mayor, Congress has the supreme authority over the city and district, which results in citizens having less self-governance than residents of the states. In addition to lacking full self-governance, the residents of the District also lack full congressional representation.

The centers of all three branches of the U.S. federal government are in the District. It also serves as the headquarters for the World Bank, the International Monetary Fund, the Organization of American States, the Inter-American Development Bank, and other national and international institutions. Washington is the frequent location of large political demonstrations and protests, particularly on the National Mall. Furthermore, Washington is the site of numerous national landmarks, monuments and museums, and it is a popular destination for tourists.

It is commonly known as D.C., The District, or simply Washington. Historically, it was called the Federal City or Washington City. To avoid confusion with the state of Washington, located in the Pacific Northwest, the city is often called simply D.C.. The population of the District of Columbia, as of 2005 U.S. Census Bureau estimates, is 582,049 persons. The great in-migration of professionals from all over the U.S. to the Washington, DC area over the past century makes meeting a native-born Washingtonian a rare occasion in some settings.

The Washington Metropolitan Area surpasses 5 million persons in population, and the Baltimore-Washington Metropolitan Area surpasses 8 million. If Washington, D.C. were a state, it would rank last in area behind Rhode Island, 50th in population ahead of Wyoming, first in population density ahead of New Jersey, and 35th in Gross State Product.