The Spring Mobilization Committee to End the War in Vietnam, which became the National Mobilization Committee to End the War in Vietnam, was a coalition of American antiwar activists formed in November 1966 to organize large demonstrations in opposition to the Vietnam War. The organization was informally known as "the Mobe".

An anti-war movement is a social movement, usually in opposition to a particular nation's decision to start or carry on an armed conflict. The term anti-war can also refer to pacifism, which is the opposition to all use of military force during conflicts, or to anti-war books, paintings, and other works of art. Some activists distinguish between anti-war movements and peace movements. Anti-war activists work through protest and other grassroots means to attempt to pressure a government to put an end to a particular war or conflict or to prevent it in advance.