Ronald Wilson Reagan (February 6, 1911 – June 5, 2004) was an American politician and actor who served as the 40th president of the United States from 1981 to 1989. A member of the Republican Party, he became an important figure in the American conservative movement, and his presidency is known as the Reagan era.

Born and raised in Illinois, Reagan graduated from Eureka College in 1932 and was hired the next year as a sports broadcaster in Iowa. In 1937, he moved to California where he became a well-known film actor. During his acting career, Reagan was elected president of the Screen Actors Guild twice, serving from 1947 to 1952 and from 1959 to 1960. In the 1950s, he became the host for General Electric Theater and also worked as a motivational speaker for General Electric. Subsequently, Reagan's "A Time for Choosing" speech during the 1964 U.S. presidential election launched his rise as a leading conservative figure. After being elected governor of California in 1966, he raised the state taxes, turned the state budget deficit into a surplus and implemented harsh crackdowns on university protests. Following his loss to Gerald Ford in the 1976 Republican Party presidential primaries, Reagan won the Republican Party's nomination and then a landslide victory over President Jimmy Carter in the 1980 presidential election.

In his first term as U.S. president, Reagan began implementing "Reaganomics", which involved economic deregulation and cuts in both taxes and government spending during a period of stagflation. On the world stage, he escalated the arms race, transitioned Cold War policy away from the policies of détente with the Soviet Union, and ordered the 1983 invasion of Grenada. Within the same period, Reagan also survived an assassination attempt, fought public-sector labor unions, expanded the war on drugs, and was slow to respond to the growing AIDS epidemic. In the 1984 presidential election, he defeated Carter's former vice president, Walter Mondale, in another landslide victory. Foreign affairs dominated Reagan's second term, including the 1986 bombing of Libya, the secret and illegal sale of arms to Iran to fund the Contras, and a more conciliatory approach in talks with Soviet leader Mikhail Gorbachev culminating in the Intermediate-Range Nuclear Forces Treaty.

Reagan left the presidency in 1989 with the American economy having seen a significant reduction of inflation, the unemployment rate having fallen, and the U.S. having entered its then-longest peacetime expansion. At the same time, the national debt had nearly tripled since 1981 as a result of his cuts in taxes and increased military spending, despite cuts to domestic discretionary spending. Reagan's policies also contributed to the end of the Cold War and the end of Soviet communism. Alzheimer's disease hindered Reagan post-presidency, and his physical and mental capacities gradually deteriorated, ultimately leading to his death in 2004. Historical rankings of U.S. presidents have typically placed Reagan in the upper tier, and his post-presidential approval ratings by the general public are usually high.