中立国指在发生武装冲突时，对交战的任何一方都不采取敌对行动的国家，分为战时中立国和永久中立国两种。中立国的权利和义务在海牙第五公约《中立国和人民在陆战中的权利和义务公约》和第十三公约《关于中立国在海战中的权利和义务公约》中作出了规定。

在冲突里中立属于一种主权受限，和不结盟是有区别的。

许多国家在第二次世界大战时宣布中立。但二战中大部分中立国都被占领，二战末期全欧洲只剩爱尔兰、瑞典、瑞士、列支敦士登、土耳其仍维持中立。后来有人质疑这几个国家当时的中立性，认为爱尔兰秘密参与同盟国，瑞典、瑞士和土耳其与纳粹德国有微妙的关系。

A neutral country in a particular war is a sovereign state which officially declares itself to be neutral towards the belligerents. A non-belligerent state does not need to be neutral. The rights and duties of a neutral power are defined in Sections 5 and 13 of the Hague Convention of 1907. A permanently neutral power is a sovereign state which is bound by international treaty to be neutral towards the belligerents of all future wars. An example of a permanently neutral power is Switzerland. The concept of neutrality in war is narrowly defined and puts specific constraints on the neutral party in return for the internationally recognised right to remain neutral.