Tammany Hall, also known as the Society of St. Tammany, the Sons of St. Tammany, or the Columbian Order, was an American political organization founded in 1786 and incorporated on May 12, 1789, as the Tammany Society. It became the main local political machine of the Democratic Party and played a major role in controlling New York City and New York State politics, and helped immigrants, most notably the Irish, rise in American politics from the 1850s into the 1960s. Tammany usually controlled Democratic nominations and political patronage in Manhattan for over 100 years following the mayoral victory of Fernando Wood in 1854, and used its patronage resources to build a loyal, well-rewarded core of district and precinct leaders; after 1850, the vast majority were Irish Catholics due to mass immigration from Ireland during and after the Irish Famine of the late 1840s.

In the politics of representative democracies, a political machine is a party organization that recruits its members by the use of tangible incentives and that is characterized by a high degree of leadership control over member activity. The machine's power is based on the ability of the boss or group to get out the vote for their candidates on election day.