The Twenty-fifth Amendment (Amendment XXV) to the United States Constitution deals with presidential succession and disability.

It clarifies that the vice president becomes president if the president dies, resigns, or is removed from office, and establishes how a vacancy in the office of the vice president can be filled.

It also provides for the temporary transfer of the president's powers and duties to the vice president, either on the initiative of the president 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 acting president until the presidential powers and duties are returned to the president.

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

The vice president of the United States (VPOTUS) is the second-highest officer 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 Senate deliberations at any time, but may not vote except to cast a tie-breaking vote. The vice president is indirectly elected together with the president to a four-year term of office by the people of the United States through the Electoral College.The modern vice presidency is a position of significant power and is widely seen as an integral part of a president's administration. While the exact nature of the role varies in each administration, 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 National Security Council and thus plays a significant role in 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 role of the vice presidency has changed dramatically since the office was created during the 1787 Constitutional Convention. Originally something of an afterthought, the vice presidency was considered an insignificant office for much of the nation's history, especially after the Twelfth Amendment meant that vice presidents were no longer the runners-up in the presidential election. The vice president's role began steadily growing in importance during the 1930s, with the Office of the Vice President being created in the executive branch in 1939, and has since grown much further. Due to its increase in power and prestige, the vice presidency is now often considered to be a stepping stone to the presidency. Since the 1970s, the vice president has been afforded an official residence at Number One Observatory Circle.

The Constitution does not expressly assign the vice presidency to a branch of the government, causing a dispute among scholars about which branch the office belongs to (the executive, the legislative, both, or neither). The modern view of the vice president as an officer of the executive branch—one isolated almost totally from the legislative branch—is due in large part to the assignment of executive authority to the vice president by either the president or Congress. Nevertheless, modern vice presidents have often previously served in Congress, and are often tasked with helping to advance an administration's legislative priorities.

Kamala Harris is the 49th and current vice president of the United States. She is the first African American, first Asian American, and first female occupant of the office. She assumed office on January 20, 2021.