Jeffersonian democracy, named after its advocate Thomas Jefferson, was one of two dominant political outlooks and movements in the United States from the 1790s to the 1820s. The Jeffersonians were deeply committed to American republicanism, which meant opposition to what they considered to be elitism, opposition to corruption, and insistence on virtue, with a priority for the "yeoman farmer", "planters", and the "plain folk". They were antagonistic to the elitism of merchants, bankers, and manufacturers, distrusted factory work, and strongly opposed and were on the watch for supporters of the British Westminster system. They believed farmers made the best citizens and they welcomed opening up new low-cost farmland, especially the Louisiana Purchase of 1803.

The term was commonly used to refer to the Democratic-Republican Party, formally named the "Republican Party", which Jefferson founded in opposition to the Federalist Party of Alexander Hamilton. At the beginning of the Jeffersonian era, only two states, Vermont and Kentucky, established universal white male suffrage by abolishing property requirements. But by the end of the Jeffersonian period, more than half of the states had followed suit, including virtually all of the states in the Old Northwest. States then moved on to allowing white male popular votes for presidential elections, canvassing voters more modernly. Jefferson's party was then in full control of the apparatus of government – from the state legislature and city hall to the White House.

Jeffersonian democracy persisted as an element of the Democratic Party until the early 20th century, exemplified in the rise of Jacksonian democracy and the three presidential candidacies of William Jennings Bryan.

Thomas Jefferson has been called "the most democratic of the founders". The Jeffersonians advocated a narrow interpretation of the Constitution's Article I provisions granting powers to the federal government. They strenuously opposed the Federalist Party, led by Treasury Secretary Alexander Hamilton. President George Washington generally supported Hamilton's program for a financially strong national government. The election of Jefferson in 1800, which Jefferson labeled "the revolution of 1800", brought in the Presidency of Thomas Jefferson and the permanent eclipse of the Federalists, apart from the Supreme Court.

Jeffersonian democracy is an umbrella term; some factions favored some positions more. While principled, with vehemently held core beliefs, the Jeffersonians had factions that disputed the true meaning of their creed. For example, during the Anglo-American War of 1812, it became apparent that independent state militia units were inadequate for conducting a serious war against a major country. The new Secretary of War John C. Calhoun, a Jeffersonian, proposed to build up the Army. With the support of most Republicans in Congress, Calhoun got his way. However, the "Old Republican" faction, claiming to be true to the Jeffersonian Principles of '98, fought him and reduced the size of the Army after Spain sold Florida to the U.S.

Historians characterize Jeffersonian democracy as including the following core ideals:

The Jeffersonians also had a distinct foreign policy:

Territorial expansion of the United States was a major goal of the Jeffersonians because it would produce new farm lands for yeomen farmers. The Jeffersonians wanted to integrate the Indians into American society or remove further west those tribes that refused to integrate. However, Sheehan (1974) argues that the Jeffersonians, with the best of goodwill toward the Indians, destroyed their distinctive cultures with their misguided benevolence.