Ronald Reagan's tenure as the 40th president of the United States began with his first inauguration on January 20, 1981, and ended on January 20, 1989. Reagan, a Republican from California, took office following his landslide victory over Democrat incumbent president Jimmy Carter and independent congressman John B. Anderson in the 1980 presidential election. Four years later, in the 1984 presidential election, he defeated former Democratic vice president Walter Mondale, to win re-election in a larger landslide. Due to U.S. Constitutional law, Reagan was limited to two terms and was succeeded by his vice president, George H. W. Bush, who won the 1988 presidential election. Reagan's 1980 landslide election resulted from a dramatic conservative shift to the right in American politics, including a loss of confidence in liberal, New Deal, and Great Society programs and priorities that had dominated the national agenda since the 1930s.

Ronald Wilson Reagan 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, his presidency constituted the Reagan era, and he is considered one of the most prominent conservative figures in American history.