The anti-war movement is a social movement against the initiation, continuation, or escalation of specific wars, especially wars that are perceived to be unjust. The anti-war movement has included activities such as protests, marches, rallies, civil disobedience, and other forms of nonviolent direct action. It has also included efforts to oppose government policies related to particular wars and to promote peaceful resolution of conflicts.

The anti-war movement began in the 1960s in response to the Vietnam War and has continued into the 21st century with opposition to the Iraq War and other conflicts. It has been made up of a variety of individuals and organizations from different political backgrounds and ideologies. The movement has been both international in scope and diverse in its goals. While some participants have focused on ending particular wars or preventing their escalation, others have sought broader social change through opposing militarism and war-making more generally.