The policy of neutrality was adopted by Ireland's Oireachtas at the instigation of the Taoiseach Éamon de Valera upon the outbreak of World War II in Europe. It was maintained throughout the conflict, in spite of several German air raids by aircraft that missed their intended British targets, and attacks on Ireland's shipping fleet by Allies and Axis alike. Possibilities of both German and British invasions were discussed in the Dáil. Both eventualities were prepared for, although most detailed preparations were done with the Allies under Plan W. De Valera's ruling party, Fianna Fáil, supported his neutral policy for the duration of the war.

A neutral country is a state that is neutral towards belligerents in a specific war or holds itself as permanently neutral in all future conflicts. As a type of non-combatant status, nationals of neutral countries enjoy protection under the law of war from belligerent actions to a greater extent than other non-combatants such as enemy civilians and prisoners of war. Different countries interpret their neutrality differently: some, such as Costa Rica have demilitarized, while Switzerland holds to "armed neutrality", to deter aggression with a sizeable military, while barring itself from foreign deployment.