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. Since the passage of the Twenty-fifth Amendment (in 1967) to the US Constitution, the vice president may also be appointed by the president to fill a vacancy, via majority confirmation by both the Senate and the House.

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, many 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.