Assistant Secretary of State (A/S) is a title used for many executive positions in the United States Department of State, ranking below the under secretaries. A set of six assistant secretaries reporting to the under secretary for political affairs manage diplomatic missions within their designated geographic regions, plus one assistant secretary dealing with international organizations and one equivalent as the coordinator/ambassador at large for counterterrorism. Assistant secretaries usually manage individual bureaus of the Department of State. When the manager of a bureau or another agency holds a title other than assistant secretary, such as "director", it can be said to be of "assistant secretary equivalent rank". Assistant secretaries typically have a set of deputies, referred to as deputy assistant secretaries (DAS).

The United States Department of State (DOS), or simply the State Department, is an executive department of the U.S. federal government responsible for the country's foreign policy and relations. Equivalent to the ministry of foreign affairs of other nations, its primary duties are advising the U.S. president on international relations, administering diplomatic missions, negotiating international treaties and agreements, and representing the U.S. at the United Nations. The department is headquartered in the Harry S Truman Building, a few blocks from the White House, in the Foggy Bottom neighborhood of Washington, D.C.; "Foggy Bottom" is thus sometimes used as a metonym.