The American Revolution was the political upheaval during the last half of the 18th century in which the Thirteen Colonies among the possessions in North America of the Kingdom of Great Britain at first rejected the governance of the Parliament of Great Britain, and later the British monarchy itself, to become the sovereign United States of America. During this period, the colonies first rejected the authority of the Parliament to govern them without representation, expelled all royal officials and by 1774 set up thirteen Provincial Congresses or equivalent to form individual self-governing states. Through representatives sent in 1775 to the Second Continental Congress, they originally joined together to defend their respective self-governance and manage the armed conflict against the British known as the American Revolutionary War (1775–83, also American War of Independence). Ultimately, the states collectively determined that the British monarchy, by acts of tyranny, could no longer legitimately claim their allegiance. They then united to form one nation, breaking away from the British Empire in July 1776 when the Congress issued the Declaration of Independence, rejecting the monarchy on behalf of the United States of America. The war ended with effective American victory in October 1781, followed by formal British abandonment of any claims to the United States with the Treaty of Paris in 1783.

The American Revolution commenced a series of intellectual, political, and social shifts in early American society and government. The development of republicanism in the United States was particularly significant, including the installation of a representative government responsible to the will of the people, thus rejecting the plutocracies of the inherited aristocracies in Europe at the time. However, sharp political debates broke out over the level of democracy desirable in the new government, with a number of Founders fearing mob rule.

The basic issues of national governance were settled with the unanimous ratification in 1788 of the Constitution of the United States (written in 1787), which replaced the relatively weak Articles of Confederation (ratified 1781) that framed the first attempt at a national government. In contrast to the loose confederation, the Constitution established a relatively powerful federated government. The United States Bill of Rights (1791), comprising the first 10 constitutional amendments, quickly followed. It guaranteed many natural rights that were influential in justifying the revolution, attempting to balance a strong national government with relatively broad personal liberties. The American shift to republicanism, and the gradually increasing democracy, caused an upheaval of the traditional social hierarchy and created the ethic that has formed a core of political values in the United States.

The American Revolution was a period during the last half of the 18th century in which the Thirteen Colonies gained independence from the British Empire and became the United States of America. In this period, the colonies united against the British Empire and entered into the armed conflict known as the American Revolutionary War (or the "American War of Independence"), between 1775 and 1783. This resulted in the United States Declaration of Independence in 1776, and victory on the battlefield in October 1781.