Opposition to the Iraq War significantly occurred worldwide, both before and during the initial 2003 invasion of Iraq by a United States–led coalition, and throughout the subsequent occupation. Individuals and groups opposing the war include the governments of many nations which did not take part in the invasion, including both its land neighbors Canada and Mexico, its NATO allies in Europe such as France and Germany, as well as China and Indonesia in Asia, and significant sections of the populace in those that took part in the invasion. Opposition to the war was also widespread domestically.
Rationales for opposition include the belief that the war is illegal according to the United Nations Charter, or would contribute to instability both within Iraq and the wider Middle East. Critics have also questioned the validity of the war's stated objectives, such as a supposed link between the country's Ba'athist government and the September 11, 2001 attacks on the United States, and its possession of weapons of mass destruction "certified" by the Niger uranium forgeries. The latter was claimed by the United States during the run-up to the war, but no such weapons were ever found.
Within the United States, popular opinion on the war has varied significantly with time. Although there was significant opposition to the idea in the months preceding the attack, polls taken during the invasion showed that a majority of US citizens supported their government's action. However, public opinion had shifted by 2004 to a majority believing that the invasion was a mistake, and has remained so since then. There has also been significant criticism of the war from US politicians such as Bernie Sanders, national security and military personnel, including generals such as Anthony Zinni and Paul Eaton who served in the war and have since spoken out against its handling, including calling for former Secretary of Defense Donald Rumsfeld resignation. Lieutenant General Gregory S. Newbold, openly critical of Rumsfeld's plans for the invasion of Iraq, resigned in protest prior to the invasion.