List of protests and demonstrations in the United States by size

The right to assemble is recognized as a human right and protected in the First Amendment of the US Constitution under the clause, "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."

Widespread mass protest became a distinct characteristic of American civic engagement during the late 20th and early 21st centuries. The rate of mass protests has risen exponentially since the mid-2010s thanks in part to the sudden and widespread availability of smartphones as well as the social media revolution, which has allowed for instant and widespread communication and planning. Each of the top ten attended protests in the United States has occurred since 1970 and three of the top five have occurred since the start of the first Donald Trump administration in 2017.