The Republican Party is one of the two major contemporary political parties of the United States, along with the Democratic Party. It is often referred to as the Grand Old Party or the GOP.

Founded in 1854 by anti-slavery expansion activists and modernizers, the Republican Party quickly surpassed the Whig Party as the principal opposition to the Democratic Party. In 1860, it came to power with the election of Abraham Lincoln to the presidency. The party presided over the American Civil War and Reconstruction and was harried by internal factions and scandals toward the end of the 19th century.

Today, the party supports a conservative platform (from an American political perspective), with further foundations in economic liberalism, supply-side fiscal policies, and social conservatism.

The current U.S. President, George W. Bush, is the 19th Republican to hold that office. Republicans currently fill a minority of seats in both the United States Senate and the House of Representatives, hold a minority of state governorships, and control a minority of state legislatures.

The party's presumptive nominee for President in the upcoming 2008 election is Senator John McCain of Arizona. It is currently the second largest party with 55 million registered members, encompassing roughly one-third of the electorate.