Conservatism in the United States is based on a belief in limited government, individualism, traditionalism, republicanism, and limited federal governmental power in relation to U.S. states. It is one of two major political ideologies of the United States. Conservative and Christian media organizations and American conservative figures are influential, and American conservatism is a large and mainstream ideology in the Republican Party and nation. As of 2021, 36 percent of Americans consider themselves conservative, according to polling by Gallup, Inc.

American political ideologies conventionally align with the left–right political spectrum, with most Americans identifying as conservative, liberal, or moderate. Contemporary American conservatism includes social conservatism and fiscal conservatism. The former ideology developed as a response to communism and the civil rights movement, while the latter developed as a response to the New Deal. Contemporary American liberalism includes social liberalism and progressivism, developing during the Progressive Era and the Great Depression. Besides conservatism and liberalism, the United States has a notable libertarian movement, developing during the mid-20th century as a revival of classical liberalism. Historical political movements in the United States have been shaped by ideologies as varied as republicanism, populism, separatism, fascism, socialism, monarchism, and nationalism.