共和党(Republican Party)，亦称老大党（Grand Old Party; GOP）。
美国两大政党之一。1854年由前辉格党、民主党和自由土壤党人组成。他们取这个名称是为了重温杰佛逊的共和主义，将国家利益置於局部利益和各州的权利之上。这个新政党反对奴隶制，反对堪萨斯-内布拉斯加法推出的将奴隶制向新的领地扩展。1856年它的第一任总统候选人弗里蒙特在十一个州取得了胜利；1860年，它的第二位总统候选人林肯则以十八个州的选举人票当选总统。美国南北战争中共和党与联邦军的胜利使它在相当长的时期内占有优势。1860～1932年间的十八次总统选举中共和党赢得了十四次，他们取得北方各州以及中西部农场主和大企业利益集团的联合支援。罗斯福任总统期间产生出共和党的进步派，使该党发生分裂，把控制权交给了民主党（1913～1921）。1933～1953年间，共和党无力对付大萧条带来的影响，使它失去了领导权。直到艾森豪任总统期间温和派声望日高，但共和党的纲领还是保守的。它采取坚决反共产主义的立场，减少政府对经济的管制，降低赋税，阻止民权立法。共和党获得中产阶级郊区居民以及受到1960年代民主党反对种族隔离政策干扰的南方白人新的支援。尼克森输掉了1960年的总统竞选；1964年保守派再次获得共和党的控制权，但他们的候选人高华德却失败了。尼克森以微弱的优势赢得了1968年的总统选举，但1972年由於水门事件而於1974年辞职。雷根（1980、1984）与他的副总统布希（1988）的竞选成功使保守派再次控制了共和党。1992年民主党的柯林顿当选总统，但1994年共和党在四十年内第一次重获国会的控制权。
English version：
Republican Party
One of two major U.S. political parties. It was formed in 1854 by former members of the Whig, Democratic, and Free Soil parties who chose the party's name to recall the Jeffersonian Republicans' concern with the national interest above sectional interests and states' rights. The new party opposed slavery and its extension into the territories, as provided by the Kansas-Nebraska Act. Its first presidential candidate, John C. Fremont, won 11 states in 1856; its second, Abraham Lincoln, won the 1860 election by carrying 18 states. Its association with the Union victory in the American Civil War allowed it a long period of dominance. Republican candidates won 14 of 18 presidential elections between 1860 and 1932, through support from an alliance of northern and midwestern farmers and big-business interests. The presidency of Theodore Roosevelt produced a progressive wing of the party, which divided it and gave control to the Democrats 1913-21. The party's inability to counter the impact of the Great Depression led to its ouster from power (1933-53) until Dwight D. Eisenhower's presidency brought a moderate wing to prominence. But the party's platform remained conservative, calling for a strong anti-Communist stance, a reduction of government regulation of the economy, lower taxes, and resistance to civil-rights legislation. The GOP gained new support from middle-class suburbanites and white Southerners disturbed by the integrationist stance of 1960s Democrats. Richard Nixon lost the 1960 presidential race; conservatives regained control in 1964, but their candidate, Barry Goldwater, lost. Nixon won narrowly in 1968 and by a landslide in 1972 but resigned in 1974 as a result of the Watergate scandal. Conservatives regained control of the party with the election of Ronald Reagan (1980, 1984) and his vice president, George Bush (1988). The 1992 election of Democrat William Jefferson Clinton as president was offset by the Republicans' regaining control of Congress (1994) for the first time in 40 years.