Ronald Wilson Reagan ( RAY-gn; February 6, 1911 June 5, 2004) was an American politician who served as the 40th president of the United States from 1981 to 1989. A member of the Republican Party, he previously served as the 33rd governor of California from 1967 to 1975 after a career as a Hollywood actor and union leader.

Reagan was born to a low-income family in Tampico, Illinois. He graduated from Eureka College in 1932 and began to work as a radio sports commentator in Iowa. In 1937, Reagan moved to California, where he found work as an actor and appeared in several major productions. From 1947 to 1952, Reagan served as president of the Screen Actors Guild, during which time he worked to root out alleged communist influence within it. In the 1950s, he moved to a career in television and became a spokesman for General Electric. From 1959 to 1960, he again served as president of the Screen Actors Guild. In 1964, his speech "A Time for Choosing"a campaign speech on behalf of Republican presidential nominee Barry Goldwaterearned him national attention as a new conservative figure. Building a network of supporters, Reagan was elected as governor of California in 1966. During his governorship, he raised taxes, turned the state budget deficit into a surplus, challenged the protesters at UC Berkeley, and ordered in National Guard troops during a period of protest movements.

In November 1979, Reagan announced his candidacy for the Republican nomination in the 1980 presidential election. He won the nomination and the election, defeating incumbent Democratic president Jimmy Carter. At 69 years, 349 days of age at the time of his first inauguration, Reagan was the oldest person to assume the U.S. presidency. Reagan ran for reelection in the 1984 presidential election, in which he was opposed by the Democratic nominee Walter Mondale, who had previously served as vice president under Carter. Reagan defeated him in an electoral landslide, winning the most electoral votes of any U.S. president: 525 (97.6% of the 538 votes in the Electoral College). It was one of the most lopsided presidential elections in U.S. history.Early in his presidency, Reagan began implementing new political and economic initiatives. His supply-side economics policiesdubbed "Reaganomics"advocated tax reduction, economic deregulation, and reduction in government spending. In his first term, he survived an assassination attempt, spurred the War on Drugs, invaded Grenada, and fought public-sector labor unions. Over his two terms, the economy saw a reduction of inflation from 12.5% to 4.4% and an average real GDP annual growth of 3.6%. Reagan enacted cuts in domestic discretionary spending, cut taxes, and increased military spending, which contributed to a near tripling of the federal debt. Foreign affairs dominated his second term, including the bombing of Libya, the IranIraq War, the IranContra affair, and the ongoing Cold War. In a speech in June 1987 at the Brandenburg Gate, four years after he publicly described the Soviet Union as an "evil empire", Reagan challenged Soviet General Secretary Mikhail Gorbachev to open the Berlin Wall. He transitioned Cold War policy from dtente to rollback by escalating an arms race with the USSR while engaging in talks with Gorbachev. The talks culminated in the INF Treaty, which shrank both countries' nuclear arsenals.

When Reagan left office in 1989, he held an approval rating of 68%, matching those of Franklin D. Roosevelt and later Bill Clinton as the highest ratings for departing presidents in the modern era. Although he had planned an active post-presidency, Reagan disclosed in November 1994 that he had been diagnosed with Alzheimer's disease earlier that year. His public appearances became more infrequent as the disease progressed. Reagan died at his home in Los Angeles on June 5, 2004. His tenure constituted a realignment toward conservative policies in the United States known as the Reagan Era, and he is often considered a conservative icon. Evaluations of his presidency among historians and the general public place him among the upper tier of American presidents.

The president of the United States (POTUS) is the head of state and head of government of the United States of America. The president directs the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces.

The power of the presidency has grown substantially since the office's establishment in 1789. While presidential power has ebbed and flowed over time, the presidency has played an increasingly strong role in American political life since the beginning of the 20th century, with a notable expansion during the presidency of Franklin D. Roosevelt. In contemporary times, the president is also looked upon as one of the world's most powerful political figures as the leader of the only remaining global superpower. As the leader of the nation with the largest economy by nominal GDP, the president possesses significant domestic and international hard and soft power.

Article II of the Constitution establishes the executive branch of the federal government and vests the executive power in the president. The power includes the execution and enforcement of federal law and the responsibility to appoint federal executive, diplomatic, regulatory, and judicial officers. Based on constitutional provisions empowering the president to appoint and receive ambassadors and conclude treaties with foreign powers, and on subsequent laws enacted by Congress, the modern presidency has primary responsibility for conducting U.S. foreign policy. The role includes responsibility for directing the world's most expensive military, which has the second largest nuclear arsenal.

The president also plays a leading role in federal legislation and domestic policymaking. As part of the system of checks and balances, Article I, Section 7 of the Constitution gives the president the power to sign or veto federal legislation. Since modern presidents are also typically viewed as the leaders of their political parties, major policymaking is significantly shaped by the outcome of presidential elections, with presidents taking an active role in promoting their policy priorities to members of Congress who are often electorally dependent on the president. In recent decades, presidents have also made increasing use of executive orders, agency regulations, and judicial appointments to shape domestic policy.

The president is elected indirectly through the Electoral College to a four-year term, along with the vice president. Under the Twenty-second Amendment, ratified in 1951, no person who has been elected to two presidential terms may be elected to a third. In addition, nine vice presidents have become president by virtue of a president's intra-term death or resignation. In all, 45 individuals have served 46 presidencies spanning 58 full four-year terms.Joe Biden is the 46th and current president of the United States, having assumed office on January 20, 2021.