A demonstration is an historically and geographically common form of nonviolent action by groups of people. The term "demonstration" was coined in the United States during the civil rights movement of the 1950s-1970s and refers to the public display of the common opinion of a group of people, a concept developed by Mahatma Gandhi during the Indian independence movement and by Martin Luther King, Jr. during the American civil rights movement. Demonstrations are a form of activism, usually taking the form of a public gathering of people in a rally or walking in a march. At times, more interventionist actions such as blockades and sit-ins have been referred to as demonstrations. Thus, the opinion is demonstrated to be significant by gathering in a crowd associated with that opinion.

Demonstrations can be used to show a viewpoint (either positive or negative) regarding a public issue, especially relating to a perceived grievance or social injustice. A demonstration is usually considered more successful if more people participate. Topics of demonstrations often deal with political, economic, and social issues.