The vice president of the United States (VPOTUS, or informally, veep) is the second-highest ranking office in the executive branch of the U.S. federal government, after the president of the United States, and ranks first in the presidential line of succession. The vice president is also an officer in the legislative branch, as the president of the Senate. In this capacity, the vice president is empowered to preside over the United States Senate, but may not vote except to cast a tie-breaking vote. The vice president is indirectly elected at the same time as the president to a four-year term of office by the people of the United States through the Electoral College, but the electoral votes are cast separately for these two offices. Following the passage in 1967 of the Twenty-fifth Amendment to the US Constitution, a vacancy in the office of vice president may be filled by presidential nomination and confirmation by a majority vote in both houses of Congress.

The modern vice presidency is a position of significant power and is widely seen as an integral part of a president's administration. The presidential candidate selects the candidate for the vice presidency as their running mate in the lead-up to the presidential election. While the exact nature of the role varies in each administration, since the vice president's service in office is by election, the president cannot dismiss the vice president, and the personal working-relationship with the president varies, most modern vice presidents serve as a key presidential advisor, governing partner, and representative of the president. The vice president is also a statutory member of the United States Cabinet and United States National Security Council and thus plays a significant role in executive government and national security matters. As the vice president's role within the executive branch has expanded, the legislative branch role has contracted; for example, vice presidents now preside over the Senate only infrequently.

The Twenty-fifth Amendment (Amendment XXV) to the United States Constitution addresses issues related to presidential succession and disability.

It clarifies that the vice president becomes president if the president dies, resigns, or is removed from office by impeachment. It also establishes the procedure for filling a vacancy in the office of the vice president. Additionally, the amendment provides for the temporary transfer of the president's powers and duties to the vice president, either on the president's initiative alone or on the initiative of the vice president together with a majority of the president's cabinet. In either case, the vice president becomes the acting president until the president's powers and duties are restored.

The amendment was submitted to the states on July 6, 1965, by the 89th Congress, and was adopted on February 10, 1967, the day the requisite number of states (38) ratified it.

Text and effect

Section 1: Presidential succession

Section 1 clarifies that in the enumerated situations the vice president becomes president, instead of merely assuming the powers and duties of the presidency as acting president. It operates automatically, without needing to be explicitly invoked.^: 108

Section 2: Vice presidential vacancy

Section 2 provides a mechanism for filling a vacancy in the vice presidency. Before the Twenty-fifth Amendment, a vice-presidential vacancy continued until a new vice president took office at the start of the next presidential term; the vice presidency had become vacant several times due to death, resignation, or succession to the presidency, and these vacancies had often lasted several years.

Section 3: President's declaration of inability

Section 3 allows the president to voluntarily transfer presidential authority to the vice president (for example, in anticipation of a medical procedure) by declaring in writing his inability to discharge the presidency's powers and duties.