The president pro tempore of the United States Senate is the second-highest-ranking official of the United States Senate, after the vice president. According to Article One, Section Three of the United States Constitution, the vice president of the United States is the president of the Senate, and the Senate must choose a president pro tempore to act in the vice president's absence.

The United States Senate is the upper chamber of the United States Congress. The United States Senate and the lower chamber of Congress, the United States House of Representatives, comprise the federal bicameral legislature of the United States. Together, the Senate and the House maintain authority under Article One of the U.S. Constitution to pass or defeat federal legislation. The Senate has exclusive power to confirm U.S. presidential appointments, approve or reject treaties, and try cases of impeachment brought by the House. The Senate and the House provide a check and balance on the powers of the executive and judicial branches of government.