The United States Senate is the upper house of the bicameral United States Congress, the lower house being the House of Representatives. The composition and powers of the Senate and the House are established in Article One of the Constitution (which does not use the terms "upper" and "lower"). Each U.S state is represented by two senators, regardless of population. This ensures equal representation of each state in the Senate. U.S. Senators serve staggered six-year terms. The chamber of the United States Senate is located in the north wing of the Capitol building, in Washington, D.C., the national capital. The House of Representatives convenes in the south wing of the same building.

The Senate has several exclusive powers not granted to the House, including consenting to treaties as a precondition to their ratification and consenting or confirmation of appointments of Cabinet secretaries, federal judges, other federal executive officials, military officers and other federal uniformed officers, as well as the impeachment trials of federal officials. The Senate is a more deliberative body than the House of Representatives because the Senate is smaller and its members serve longer terms, allowing for a more collegial and less partisan atmosphere that is somewhat more insulated from public opinion than the House. The Senate is considered a more prestigious body than the House of Representatives on account of its longer terms, smaller membership, and larger constituencies.

The Framers of the Constitution created a bicameral Congress first and foremost as a compromise between those who felt that each State, since it was Sovereign, should be equally represented, and those who felt the Legislature must directly represent the People, as did the House of Commons in England. Secondly, there was a desire to have two Houses that could act as an internal check on each other. One was intended to be a "People's House" directly elected by the People, and with short terms obliging the Representatives to remain close to their constituents. The other was intended to represent the States insomuch as they retained their sovereignties not expressly delegated to the National government. The Constitution provides that the approval of both chambers is necessary for the passage of legislation.