Opposition to NATO tends to mainly come from pacifist organizations, workers movements, environmental groups and green parties, and socialist/communist political parties.
Many of them believe NATO to be antithetical to global peace and stability, environmentally destructive, and an obstacle to nuclear disarmament.
There are also libertarian and far-right political parties who oppose NATO, believing it to be antithetical to the ideals of limited government, non-interventionism and anti-globalization.