The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washington, D.C. Senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a governor's appointment. Congress has 535 voting members: 100 senators and 435 representatives. The U.S. vice president has a vote in the Senate only when senators are evenly divided. The House of Representatives has six non-voting members.

A legislature is a deliberative assembly with the legal authority to make laws for a political entity such as a country, nation or city. They are often contrasted with the executive and judicial powers of government. Legislatures can exist at different levels of government–national, state/provincial/regional, local, even supranational. Countries differ as to what extent they grant deliberative assemblies at the subnational law-making power, as opposed to purely administrative responsibilities.