Benjamin Harrison's tenure as the president of the United States lasted from March 4, 1889, until March 4, 1893. Harrison, a Republican from Indiana, took office as the 23rd United States president after defeating Democratic incumbent President Grover Cleveland in the 1888 election. Four years later he was defeated for re-election by Cleveland in the 1892 presidential election, and became the first U.S. president to be succeeded in office by his predecessor.

Harrison and the Republican-controlled 51st United States Congress (derided by Democrats as the "Billion Dollar Congress") enacted the most ambitious domestic agenda of the late-nineteenth century. Hallmarks of his administration include the McKinley Tariff, which imposed historic protective trade rates, and the Sherman Antitrust Act, which empowered the federal government to investigate and prosecute trusts. Due in large part to surplus revenues from the tariffs, federal spending reached one billion dollars for the first time during his term. Harrison facilitated the creation of the National Forests through an amendment to the General Revision Act (1891), and substantially strengthened and modernized the United States Navy. He proposed, in vain, federal education funding as well as voting rights enforcement for African Americans in the South. Harrison's presidency saw the addition of six new states, more than any other president. In foreign affairs, Harrison vigorously promoted American exports, sought tariff reciprocity in Latin America, and worked to increase U.S. influence across the Pacific.

The initial favorite for the Republican nomination in the 1888 presidential election was James G. Blaine, the party's nominee in the 1884 presidential election. After Blaine wrote several letters denying any interest in the nomination, his supporters divided among other candidates, with John Sherman of Ohio as the leader among them. Others, including Chauncey Depew of New York, Russell Alger of Michigan, and Walter Q. Gresham, a federal appellate judge, also sought the delegates' support at the 1888 Republican National Convention. Blaine did not publicly endorse any of the candidates as a successor; however, on March 1, 1888, he privately wrote that "the one man remaining who in my judgment can make the best one is Benjamin Harrison."

Harrison represented Indiana in the United States Senate from 1881 to 1887, but lost his 1886 bid for re-election. In February 1888, Harrison announced his candidacy for the Republican presidential nomination, declaring himself a "living and rejuvenated Republican." He placed fifth on the first ballot at the 1888 Republican convention, with Sherman in the lead; the next few ballots showed little change. The Blaine supporters shifted their support among different candidates, and when they shifted to Harrison, they found a candidate who could attract the votes of many other delegations. Harrison was nominated as the party's presidential candidate on the eighth ballot, by a count of 544 to 108 votes. Levi P. Morton of New York was chosen as his running mate.

Harrison's opponent in the general election was incumbent President Grover Cleveland. Harrison reprised the traditional front-porch campaign, which had been abandoned by Blaine in 1884. He received visiting delegations to Indianapolis and made more than ninety pronouncements from his home town; Cleveland made only one public campaign appearance. The Republicans campaigned in favor of protective tariffs, turning out protectionist voters in the important industrial states of the North. The election focused on the swing states of New York, New Jersey, Connecticut, and Harrison's home state of Indiana. Harrison and Cleveland split these four states, with Harrison winning in New York and Indiana. Voter turnout was 79.3%, reflecting a large interest in the campaign; nearly eleven million votes were cast. Although he received approximately 90,000 fewer popular votes than Cleveland, Harrison won the electoral vote 233 to 168. This was the third U.S. presidential election in which the winner lost the popular vote.

Although Harrison had made no political bargains, his supporters had given many pledges upon his behalf. When Boss Matthew Quay of Pennsylvania heard that Harrison ascribed his narrow victory to Providence, Quay exclaimed that Harrison would never know "how close a number of men were compelled to approach...the penitentiary to make him president." In the concurrent congressional elections, the Republicans increased their membership in the House of Representatives by nineteen seats, winning control of the chamber. The party also retained control of the Senate, giving one party unified control of Congress and the presidency for the first time since the 1874 elections. The Republican sweep allowed Harrison to pursue an ambitious legislative agenda in the resulting 51st Congress.

Harrison was sworn into office on March 4, 1889, by Chief Justice Melville Fuller. At 5' 6" tall, he was only slightly taller than James Madison, the shortest president, but much heavier; he was also the fourth (and last) president to sport a full beard. Harrison's inauguration ceremony took place during a rainstorm in Washington D.C. Outgoing President Grover Cleveland attended the ceremony and held an umbrella over Harrison's head as he took the oath of office. Harrison's speech was brief – half as long as that of his grandfather, William Henry Harrison, whose speech holds the record for the longest inaugural address of a U.S. president.

In his speech, Benjamin Harrison credited the nation's growth to the influences of education and religion, urged the cotton states and mining territories to attain the industrial proportions of the eastern states, and promised a protective tariff. Concerning commerce, he said, "If our great corporations would more scrupulously observe their legal obligations and duties, they would have less call to complain of the limitations of their rights or of interference with their operations." He called for the regulation of trusts, safety laws for railroad employees, aid to education, and funding for internal improvements. Harrison also urged early statehood for the territories and advocated pensions for veterans, a statement that was met with enthusiastic applause. In foreign affairs, Harrison reaffirmed the Monroe Doctrine as a mainstay of foreign policy, while urging modernization of the Navy. He also gave his commitment to international peace through noninterference in the affairs of foreign governments.